HORT 201

Agriculture

('agri' L. = field, 'cultura' L. = cultivation) - the science and technology of growing and raising plants and animals.

Benefits of biotechnology

- crop losses from pests can be devastating - consumers do not wish to eat food that has been treated with pesticides - run-off of agricultural wastes from excessive pesticide use and fertilizers can poison the water supply - growing GMO foods can help eliminate the application of chemical pesticides and reduce crop costs, and get one step closer to the ultimate goal of worldwide food security

risks of biotechnology

- crop losses not worth risk to human health and environment? - safety of technology is unknown; could genes move around to other organisms? - moral issues: should we be moving genes around in the first place? - domination of world food supply by a few large companies

primary cell wall

- first wall layer laid down in all cells - only wall layer found in young growing cells, some storage cells, Photosynthesizing cells - very thin (<1 micron) - Surrounds the protoplasm - Porous to water and minerals

Rules of Plant Nomenclature

- genus is always capitalized - species lowercase - genus and species italicized or underlined - if authority is noted, his/her last name is in parenthesis followed by a period - If the plant is a variety of a species, there are two options: variety name is written after the species name, is lower-cased and either italicized or underlined. Or it may be noted by "var." preceding - not italicized or underlined - If the plant is a cultivar, there are two options: "cv" lowercased and italicized preceding the name, or the name is in single quotations. Either way the cultivator name will be uppercase and not italicized/underlined

Leaf morphology: leaf veination

- pinnate: lateral veins extend from a central midrib - palmate: multiple major veins extend from the petiole-blade union - parallel: multiple parallel lateral veins

Challenges facing global food security

- population growth - diseases i.e. wheat rust diseases, often spread via wind, currently threaten 37% of the world's wheat - pests i.e. desert locust, which migrates across continents. In 2012, USD spent 8.2 million to help prevent modern locust plague

3 Tissue Systems that occur in plants

1) Dermal Tissue System Function: Protection from the environment and water loss. Tissues: a) epidermis - single layer of cells on primary (herbaceous ) plant parts. b) periderm or bark - a corky tissue that replaces epidermis on secondary (woody) plant parts. 2) Vascular Tissue System Function: Conduction of water, nutrients, sugars and hormones throughout the plant. Tissues: a) xylem - conducts water and nutrients up roots, stems and leaves. b) phloem - conducts water, sugar, hormones, etc. down and up roots, stems and leaves; moves from where produced (called sources) to where needed (called sinks). 3) Ground or Fundamental Tissue System Function: Storage, support, filler tissue and site of photosynthesis. Tissues: a) cortex - outer region of stems and roots. b) pith - center of stems. c) mesophyll - middle of leaves and flower petals.

Areas of Ornamental Horticulture

1) Floriculture - flowering and foliage plant culture and production 2) Floristry - floral design and retail floristry operation 3) Nursery Production - tree, shrub and vine culture and production 4) Landscape Horticulture - exterior and interior design, construction and maintenance of landscapes

Areas of Agriculture

1) Forestry - the science and technology of culturing, utilizing and improving forest trees and their products (ex. pulp, resins, oils, etc.). 2) Agronomy - the science and technology of culturing, utilizing and improving field crops (grain, fiber and forage crops). 3) Horticulture ('hortus' L. = garden, 'cultura' L. = cultivation) - the science, technology and art of culturing, utilizing and improving fruit, vegetable, flowering and ornamental plants.

CLASSICAL GUIDELINES FOR PLACEMENT OF A CROP IN HORTICULTURE, AGRONOMY OR FORESTRY

1) Intensity of Production - example strawberries vs. cotton 2) Purpose Crop is Grown - example oak or pecan trees in forest vs. landscape 3) Tradition or Custom - example sweet vs. field corn, or tobacco

Areas of Horticulture

1) Olericulture - vegetable culture and production 2) Pomology - fruit and nut culture and production 3) Ornamental Horticulture - plants grown for aesthetic uses, improvement of quality of life and our environment, and functional uses (ex: energy conservation).

Light can be affected as follows

1) absorbed - when radiant energy (such as light) is absorbed it is converted primarily to heat energy. re-radiation - heat energy is converted to radiant energy as long wavelengths in the infrared (IR) region of the spectrum. 2) transmitted - when radiant energy (such as light) passes through an object unaffected, such as glass. 3) reflected or scattered - when radiant energy (such as light) is "bounced off" an object, such as a solid colored surface. The color of an object is the color (as determined by wavelength) of light that is transmitted or reflected. In other words, your eyes see the color that is not absorbed.

3 Basic Cell Types comprise most of the tissues of plants

1) parenchyma: - thin, non-lignified primary cell walls - filler, storage, protection, photosynthesis - examples: flesh of potato, lettuce leaf 2) collenchyma: - unevenly thickened, non-lignified primary cell walls - support in growing tissues - example: strings in celery stalks 3) sclerenchyma 2 Types a) fiber b) sclereid or stone cell - evenly thickened, lignified (tough) secondary cell walls - dead at maturity - support in mature tissue - examples: fiber - bamboo cane sclereid - seed coat stone cell - pear fruit

Measurement of light intensity

1) photometer or common light meter (cheapest) - measures amount of luminance Expressed as: a) foot-candle (ft-c) - 1 lumen per square foot b) lux - 1 lumen per square meter 1 foot-candle = 10.76 lux 2) quantum sensor - measures actual light intensity or light energy in the 400-700 nm wavelength band. photosynthetically active radiation (PAR) - light intensity in the 400-700 nm wavelength band that is used by plants in photosynthesis. Expressed as a) microEinstein per second per square meter - mEs-1m-2 (400-700 nm) b) watts per square meter - Wm-2(400-700 nm) 3) radiometer - measures radiant energy received at all wavelengths, i.e. total solar radiation. 4) spectral radiometer - measures the intensity at each wavelength (i.e. color spectrum of a light).

Light has 4 properties:

1) quantity - the intensity or amount of light 2) quality - the wavelength or color of light 3) duration - determines the total amount of light energy received total amount of light energy = quantity x # hours of light 4) photoperiod- the day length, or length of light in a 24 hour cycle, regardless of quantity.

what makes plants different from say, animals or fungi

1. Multicellular: this one is pretty self-explanatory; plants are made of multiple cells. Not only more than one cell, but more than one type of cell. This is how plants differ from amoebas. 2. Eukaryotic: The cells have a nucleus which is bound by a membrane, and organelles. Look at the plant cell on the right and note the organelles are all membrane-bound. This is how plants differ from bacteria. 3. Autotrophic: This means plants can create their own food. To do that, they use photosynthesis, which takes place in an organelle in the cell called a chloroplast. This is how plants differ from animals and fungi. 4. Cell walls: This is what makes plant cells square (whereas animal cells are round); without rigid cell walls, plants would be blobs on the ground. Humans depend on skeletal systems; plants don't need that, because their cells have a cell wall made of cellulose. This is what makes plants different from animals and bacteria.

food security

A condition in which people have access to sufficient, safe, and nutritious food that meets their dietary needs for an active and healthy life. - 2000 calories a day

Plant Membrane Transport

A hormone travels from the site of synthesis to the site of its use across membranes (phospholipid bilayers) - proteins embedded into the bilayers act as pumps to move organic compounds across the membranes

Anatomy of Monocot leaf

A monocot leaf is similar to a dicot leaf, except monocot leaves have no palisade and the mesophyll is all spongy parenchyma.

plasma membrane

A selectively-permeable phospholipid bilayer forming the boundary of the cells Phospho "head" is polar and attracts water - "tail" repels water - bilayer means there are two sheets of phospholipids, oriented tail to tail with heads out Double membrane that is selectively permeable and regulates absorption into and leakage from cells

plant biotechnology

A single gene can be removed from one string and added to another

vascular tissue system

A system formed by xylem and phloem throughout a vascular plant, serving as a transport system for water and nutrients, respectively. - function: conduction of water, nutrients, sugars, and hormones throughout the plant Tissues: xylem: conducts water and nutrients up from the roots phloem: conducts water, nutrients, etc up, down, and throughout the plant from source to sink - source: the location the sugar, hormone, etc. is created - sink: the location the sugar, hormone, etc. is used

Essential Elements

An essential element is one that is required by plants for normal growth, development, and completion of its life cycle, and which cannot be substituted for by other chemical compounds. Plants require 17 essential elements: 3 supplied naturally by air and water Carbon (C), Hydrogen (H), Oxygen (O) 6 macronutrients: required at 0.1-0.6% of a plant's dry weight Nitrogen (N), Phosphorus (P), Potassium (K), Sulfur (S), Calcium (Ca), Magnesium (Mg) 8 micronutrients: required at 1-300 ppm of a plant's dry weight Iron (Fe), Zinc (Zn), Copper (Cu), Molybdenum (Mo), Boron (B), Manganese (Mn), Chlorine (Cl), and Nickel (Ni) An easy mnemonic device to remember the 17 elements: "See Hopkins Cafe, managed by my cousins Moe and Clinique" - C HOPKiNS CaFe, Mg B Mn CuZns, Mo and CliNique (Chlorine and Nickel)

How do plants grow?

At a very basic level, plants grow through cell division and elongation... but as opposed to animals, plant cell division occurs at specific locations, called a meristem. This means that not ALL of the plant cells are dividing; only the cells at the meristems. The cells that are created at the meristems are not yet differentiated - that means the cells have not yet become specialized - they can become collenchyma, parenchyma, or sclerenchyma. They may end up as vascular tissue, dermal tissue, or ground tissue. You've probably already figured out that horticulturalists like to classify everything. The same is true for meristems, which can be classified as primary or secondary . The location of the primary meristem is in one of two places - the outermost tip of a stem, or the outermost tip of a root (called apical meristem because it is at the apex of the root or stem). But wait a second. When I mow my lawn, I remove the tips of those grass stems, yet it continues to grow. Why? Because in monocots, the primary meristem is located at the base of the plant near the soil, and is called intercalary meristem. (Welcome to horticulture, where there is always an exception to every rule or classification!) Plant growth as a result of primary meristem (either apical or intercalary) is considered primary growth and mostly results in a growth in length, and gives rise to primary (herbaceous) tissues. After those cells have divided and begun to specialize into various cell types and tissue groups,they can grow in width or diameter and give rise to secondary growth (woody or corky), which occurs at lateral meristems, which are located at meristematic regions along the sides of stems and roots. These lateral meristems are located in the cambial tissue of woody plants. If you look at the vascular bundle arrangement for dicot stems, you will see a thin layer of tissue called the cambium embedded within the vascular bundles. This cambium is the location for the lateral meristems, and it is where woody plants grow in diameter. This makes sense if you think about it - if trees only had apical meristems, they would grow very tall but the trunks would never gain girth. But without the girth of the trunk, the tree would be unable to support the weight of the canopy. Take a look at the diagram below, which includes photographs of actual apical meristems (with a microscope because apical meristems are very small.

nitrogen fixation

Auburn University has an ongoing soil fertility experiment on its main campus called The Old Rotation (I swear - google it!). It's a crop rotation experiment that has been ongoing since 1896! (pictured below) Each season a new crop is planted: either cotton, winter legumes, corn, or soybeans.... and the entire field has not been fertilized since the beginning of the experiment. Why does this work? How can corn and cotton continue to be produced on the same plot of land for over 100 years without fertilizer (the control does include fertilizer, but the rotational treatments do not). It's all because of nitrogen fixation; the legumes "fix" nitrogen. (Every time I teach nitrogen fixation my inner commentary goes full-on dad joke with "but what's wrong with it?!")

5 primary plant hormones

Auxin (indoleacetic acid) Cytokinins (zeatin, zeatin riboside, isopentenyl adenine) Gibberellins (GAx...125) Abscisic acid (ABA) Ethylene

The Nitrogen Cycle

Before reading any further, take a look at the illustration below... follow the arrows and don't worry about what the words mean; just look at the pictures for now. Do you remember learning that the earth's atmosphere has a greater proportion of nitrogen than oxygen or carbon? Well that's still true. It's about 78% nitrogen and 21% oxygen, and the rest is an assortment of other molecules. But that nitrogen exists as N2; a pair of nitrogen molecules bound together. Fortunately for plants, Nitrogen is one of the most common elements on earth; unfortunately for plants, they can't use just any old form of nitrogen. That goes for atmospheric N2; plants can't use it. Plants use either ammonium (NH4), nitrate (NO3), or urea ((NH2)2CO). That's it. Any other form of Nitrogen cannot be taken up by plants. That's where nitrogen fixation comes in - that's the literal process of processing atmospheric nitrogen into a form that is usable to plants. The nitrogen is quite literally being "fixed" for plant use. While cloud-to-ground lightning strikes fix nitrogen (pretty cool), most of the nitrogen fixation on the planet is done by bacteria. Where we might we find some of those magic nitrogen-fixing bacteria? In the nodules of legume roots! Those legumes and soybeans planted at The Old Rotation have nitrogen-fixing bacteria living inside the roots; the bacteria give off nitrogen as a byproduct, so the nitrogen concentration of the soil goes up. The image shows nitrogen-fixing soil bacteria that are NOT living in the legume root nodules... those guys take care of ammonification. When a plant or animal dies or leaves organic waste behind, it contains organic nitrogen; these soil-borne bacteria convert that organic nitrogen (AKA urea) back into ammonium (NH4). At this point we're looking at the nitrification process; the image shows that ammonium (NH4) is converted to nitrite (NO2), and then to Nitrate (NO3)... it all happens very quickly by soil bacteria. But why?! I already told you that plants can use ammonium, nitrate, or urea. So... if it's already in ammonium form, why wouldn't the plants take it up through the roots before the soil organisms can convert it? High concentrations of ammonium can be toxic to plants; on top of that, the microorganisms in the soil need that ammonium, and it all ends up as nitrate, which plants use, so just don't worry about why. Still the earth turns, and plants and microorganisms live in unity. This must be a super efficient process, right? Like, why would we ever need to fertilize plants if all of this nitrogen is being processed in a continuous cycle? Because it isn't that efficient. That nitrate (NO3) in the soil isn't just taken up by plant roots. Sometimes it's subjected to denitrification before the roots can get to it. Denitrification is the conversion of nitrate in the soil to gaseous nitrogen that escapes back into the atmosphere. In short, nitrogen is volatile. It doesn't just hang out in any one form while it's waiting for a plant to eat it; it's either going to be eaten by a plant, or a bacterium, or converted into a gas where the whole process starts over again. That's why it's a cycle. It never stops.

Vernalization and Biennials

Before we can define vernalization, we should talk about biennials. You know by now that plants can be classified in almost countless ways - monocot/dicot, angiosperm/gymnosperm, etc. Plants can also be classified based on the length of their life cycle. Annuals are plants completing an entire life cycle in a single year. Those cheap 6 packs of colorful flowers for sale at garden centers are all annuals. They're inexpensive because they don't last long. Pansies, petunias, marigolds, and mums are all annuals. Biennials are plants that require two years to complete a life cycle. Typically the first year is spent on vegetative growth, then it goes dormant over winter. The second year is when reproductive growth occurs - the plant flowers and creates seeds. Many biennials reseed themselves prolifically, so in a field of biennials it's easy to assume they are either reseeding annuals or perennials, but in fact they are biennials. Foxglove, winter cabbage, and winter kale are all biennials. Perennials are plants that live longer than two years. They typically complete a vegetative/reproductive cycle each year, but not always. For example, bamboo is a perennial but each plant only flowers once and then dies; this usually occurs after 40-100 years but varies by species. On to vernalization, which is a cold treatment required to trigger or initiate a flower formation in biennials. In the example of foxglove, the plant must experience a dormant period of cold (a.k.a. winter) before bolting. Bolting is the flower formation and seed stalk elongation. Foxglove is pictured below - see how tall the flower stalks are? When that stalk begins growing, the plant has bolted.

plants exposed to blue light

Blue light helps with the plant's production of chlorophyll--the green pigment that traps light energy and is integral to photosynthesis. In other words, blue light is easier for a plant to absorb and use the energy in photosynthesis. So, blue light increases plant growth and makes the plant reach maturity faster.

High temperature extremes

Cardinal temperature is the temperature range in which (most) plants grow and survive. The maximum cardinal temperature for growth is 90 F for most species; the maximum for survival is 130 F for most species. [Yes, I know the previous page said plant cells can experience damage at 86 F, which is true, but they can still function, albeit at a decreased efficiency, up to 90 F] So how do high temperatures affect plants? Proteins denature at 130 F, so temperatures at and above that threshold will quickly result in plant death. The three ways plants dissipate excess heat is long-wave radiation, heat convection into the air, and transpiration (transpiring water out of their stomata). Transpiration is critical; when the soil becomes dry, transpiration can slow or cease. Not only does the water content of the plant's tissues decrease, but the plant loses the cooling effects of transpiration as well. Under heat-stressed conditions: Photosynthetic rates decrease Plants wilt and dessicate Above-ground portions become susceptible to sunscald (like a sunburn except on a plant - sunscald damage on a tree trunk is pictured below) If the heat stress continues, it can result in mortality. Of course this is species dependent. Some species have built-in protections against heat damage.

What pigments are yellow in color?

Carotene pigments (which are carotenoids) produce yellow, orange and red colors whereas anthocyanin pigments (which are flavonoids) produce red, purple, magenta and blue colors. Most red flowers use anthocyanin pigments to produce their red coloring (although some use carotenoids)

Vacuole

Cell organelle that stores materials such as water, salts, proteins, and carbohydrates

Plant Dormancy

Dormancy is a period of inactive growth to survive adverse conditions. There are two types of plant dormancy: Quiescence is dormancy imposed by external (i.e. hard seed coat, like a coconut husk) or environmental conditions (like extreme temperatures). It is overcome by removing the unfavorable factor Rest or Physiological Dormancy is imposed by internal (i.e. hormonal imbalances) conditions; usually the internal conditions are triggered by an environmental change, such as shorter days. It is overcome by satisfying the requirement for rest.

Factors affecting respiration

Factor Tissue age - Young tissue has a higher rate of respiration Ripening Fruit -Respiration increases as a fruit ripens Temperature - Respiration decreases as temperature decreases - Respiration ceases at freezing temperatures - Respiration increases as temperature increases until temperatures get too high, then respiration ceases with tissue mortality Oxygen - Respiration decreases as oxygen decreases - Without oxygen, anaerobic fermentation occurs Carbon Dioxide - Respiration decreases as carbon dioxide increases Wounding - Wounded, damaged, or infected tissue has a higher rate of respiration than healthy tissue Water content - Dry tissue has decreased respiration

Field Soils

Field soils are layered in horizons, as pictured below. A great acronym for remembering soil horizons in order is Our Aunt Ethel Bakes Cookies Regularly. Field soils typically refers to horizons O-B; the thickness and presence of the horizons varies by location. Regardless of the layers present, soils are formed from the bottom up: the R Horizon breaks down and becomes the C Horizon, which further weathers and becomes the B Horizon, and so on. The only exception is the O Horizon, which is formed as organic materials (animals, insects, and plants) are added to the top. The properties of the parent materials determine the properties of the top soil. Field soils can be mineral soils or organic soils. Mineral soils contain less than 20% organic matter. Organic matter is basically magic for soils. It stabilizes soil structure, increases water retention, increases drainage (yes - it makes soils hold and drain water. MAGIC), increases CEC (more on that in a bit), stabilizes pH, and provides a food source for microorganisms, earthworms, and other beneficial fauna. Mineral soils are classified based on their texture.

Middle lamella in plants

Function: holds individual cells together composition: Ca2+ and Mg2+ pectates - forms gel - pectin plentiful in unripe fruits: breaks down with ripening

Mitochondria

Function: site of respiration

conventional plant breeding

Genes are made of DNA - cross two plants to get a desired gene - creates a new plant variety, but because you transfer so many genes you tend to lose a trait - harder to control traits

Plant Hardiness Zones

Hardiness refers to a plant's ability to survive extremes in cold temperatures.There are various plant-based zone maps used worldwide, but the most commonly used plant hardiness zone map in the US was developed by the USDA. It's based on the average lowest annual temperature. A color-coded map is below

Understanding the -cot suffix

Have you ever grown a plant from a seed? Any plant, as long as it came from a seed? Did you notice how the first little baby leaves were just sort of plain looking leaves, but the newer, more mature leaves looked totally different? The picture on the right is of two tomato seedlings. The larger (older, thus first to appear) leaves are plain, generic leaves. The smaller, newer leaves look more like real tomato leaves with the funky shapes? Those baby leaves are called cotyledons- the "seed leaves". Those are literally the embryonic leaves that were inside the seed! The plant doesn't put effort into making those leaves "look like" they're supposed to -that little baby seedling just wants those cotyledons to start creating food via photosynthesis... so they're just generic, plain leaves. Baby leaves. Seed leaves. Cotyledons. Now you can probably guess that monocot means one cotyledon and dicot means two cotyledons - and you're exactly right.

Photoperiodism

Have you ever kept a poinsettia plant alive after Christmas, but it never turned red again? That's because of photoperiodism, or a plant's ability to detect the day length. Poinsettias turn red after they sense shorter days (or longer nights, depending on how you look at it). To force a poinsettia to turn red, you need to cover it and keep it in complete darkness for 14 hours a day.... but it takes several weeks. Most poinsettia producers cover their greenhouses beginning in September to "shorten" the days. They are so sensitive to day length that no light can be let in - all it takes is one interruption of the cycle, and the growers have to start over. If you don't "force" your poinsettia to turn red, it will turn on its own around February, when the days have been naturally shorter for several weeks. You know horticulturalists like to classify plants as often as possible, and so we have created a classification based on flowering response to daylength. Short Day Plants: In order to flower, the day length has to be less than 12 hours (these are usually plants that flower during the fall or winter, when the days are naturally getting shorter; chrysanthemums are an example). Long Day Plants: In order to flower, the day length must be more than 12 hours (these are usually plants that flower in the summer, when the days are naturally getting longer; hibiscus is an example) Day Neutral Plants: The plant will flower regardless of the day length

fertilizer analysis

Have you ever looked at a bag of fertilizer, or miracle grow, or weed and feed and noticed three numbers separated by dashes, like 8-8-8 or 8-2-4? That's the fertilizer analysis; a sequence of 3 numbers on a bag of fertilizer label that gives the percent composition of N-P2O5-K2O in a fertilizer; it is required by law to be on every fertilizer label. In the example above, an 8-2-4 fertilizer contains: 8% N 2% P2O5 4% K2O As you can see, the three numbers correspond to the alphabetical elements as they are spelled in full (even though K comes after P, Phosphorus comes before Potassium). Phosphorus and potassium are not stable in their pure forms, so they must be incorporated as compounds: phosphate and potash.

The Cohesion-Tension Theory

Have you ever wondered how water moves from the soil into the plant? The cohesion-tension theory describes the mechanism. If you think of transpiration (water lost through stomata) as evaporation that occurs at the surface of the leaf, then you can imagine water being pulled out of the plant through leaves. Makes sense so far. Well, water molecules cohere, or stick together. That's why when you spill water, it puddles together. Cohesion is what causes water to try to climb the sides of a glass - it creates that curved meniscus instead of being perfectly level. Given that, imagining that water is being pulled from the leaves via transpiration, you can imagine that the water sticks together via cohesion, pulling the next closest water molecule with it. That pull is tension, and is measurable as a pressure measurement. Pure water has a potential (or the pressure measurement) of 0 Mega Pascals (MPa). Comparatively, the atmosphere at 20% relative humidity has a water potential of -500 MPa. Yes - negative 500 MPa. Because water will always move towards a site with lower (or more negative) pressure, it is literally pulled out of the plant. The water in the roots pulls on the water in the soil (this is a very simplified explanation, by the way), and that supplies the water necessary for plant function, until the negative pressure in the soil is less than the pressure in the plant. That's basically what happens when soil dries out - there isn't enough water in the soil to surpass that pressure differential. The stomata remain open (unless it's CAM), and if it goes long enough, the plant starts to suffer symptoms of drought.

C:N Ratios in organic matter

Have you or anyone you know ever had a compost pile? If so, did you or they ever fertilize it? What?! Fertilize a compost pile?! Isn't that, like, totally the opposite of the point? It depends on what you've added to the pile lately. You just learned about the nitrogen cycle, and all of the little critters in the soil who convert nitrogen to usable plant forms. You learned that nitrogen is the byproduct... but they live off of carbohydrates... carbon. The C:N ratio is the ratio of carbon to nitrogen in an organic material. High C:N ratio materials are things like wood chips, sawdust, uncomposted bark... more carbon than nitrogen. Low C:N ratio materials are things like manure, fish emulsion, green grass clippings. The microorganisms will use up all of the available nitrogen while processing the carbon in a high C:N ratio organic material. That's why some compost piles need fertilizer here and there; if a storm has just blown down a tree and you've added a lot of wood chippings and branches, you're probably going to need to add some fertilizer to keep those microbes alive. The other lesson in this is that not all organic material is created equal. If you want to use a safe, organic source of nutrients for your flower bed, you better use one with a low C:N; otherwise you'll end up starving your flowers because all of the available nitrogen will go towards breaking down the organic matter you applied!

Overview of plant hormones

Hormones are chemical messengers produced in one cell that moderate cellular processes in another cell. That means most hormones are produced in one part of the plant but used in an entirely different part of the plant; and yes, you need to know the sites of production and the sites of translocation for each hormone.

CAM Metabolism Review

If C4 plants are more highly evolved than C3 plants, then CAM (crassulacean acid metabolism) plants are the most highly evolved of all. They are super cool. Imagine a cactus growing in a desert. It needs to create sugar from CO2, but every time the stomata open they are not only harvesting CO2, but they're also losing precious water. It's happening on a microscopic level, sure... but when it only rains a tenth of an inch a month, every microscopic drop really does count. Enter CAM. As opposed to C3 and C4 plants, whose stomata are open during the day and closed at night, CAM plants open the stomata at night to harvest CO2, store it overnight as malic acid, and then when the sun comes up they photosynthesize using up the malic acid with their stomata closed the entire time. Told you CAM plants are super cool. CAM metabolism also uses PEPcase instead of rubisco; the only difference is that since the sun is down, the light reactions aren't operating. Since the light reactions aren't operating, the dark reactions have no ATP or NADPH to power their processes. So, that 4-C product (malic acid) is stored in the bundle sheath cells all night until the sun comes up and the light reactions start. CAM is an evolutionary advantage specific to preventing water loss; as you could expect, many succulents are CAM plants, but pineapple plants are CAM species as well!

Climate and Global Climatic Zones

If weather is the current and temporary atmospheric condition, climate is the average atmospheric condition over a long period of time. Climate zones are determined by the position of the earth relative to the sun (see diagram) Seasons are determined by where the earth happens to be in its oval-shaped orbit around the sun as a result of the tilt of the earth's axis; the northern hemisphere is tilted towards the sun during the summer, but away from the sun during the winter. Climate zones, however, are determined by latitude. Tropical zones lie near the equator, polar zones lie near the poles, and temperate zones lie between them. Temperate zones have more seasonal variation than tropical or polar zones

Growing Media

If you buy a plant in a pot - whether it's an indoor plant or a shrub that you'll transplant into your yard - the material in which it grows is not mineral soil. In fact, it's not even organic soil. A few of the synonyms for this growing media are artificial media, soilless media, potting soil, and container media. Growing media are mostly composed of organic components, typically peat moss, but some manufacturers include composted barks, wood shavings, rice hulls, coconut coir, or leaf litter. Inorganic components can range from sand to vermiculite or perlite. Have you ever noticed the white balls in potting soil that float? That's perlite - it's a very light weight volcanic rock. The more you know dot gif. So why aren't containerized plants grown in real soils? Real soils are heavy - which increases labor and shipping costs, and it's difficult to get. Another problem is sterility - container media needs to be sterile and free of weed seed. It is far easier to sterilize (through heat or steam) a manufactured product as opposed to digging a load of soil and hoping it doesn't have any fungal spores or noxious weed seed.

macronutrients and micronutrients

If you or anyone you know has been into fitness or body building, you've probably heard the term "macros". As applied to the human diet, it generally refers to the percent of daily calories from protein, fat, or carbohydrates. Each of those three categories is a "macro". When it comes to plant nutritions, some essential elements are macronutrients, meaning plants need those elements in greater quantities compared to the micronutrients. This does NOT mean that macronutrients are more important than micronutrients, it simply means that plants need a greater quantity of macronutrients. Here's the categorization of macros vs. micros, and as usual, this is testable: Macronutrients Carbon Hydrogen Oxygen Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur Micronutrients Iron Manganese Zinc Boron Copper Molybdenum Chloride Nickel

secondary cell wall

In plant cells, a strong and durable matrix that is often deposited in several laminated layers around the plasma membrane and provides protection and support. - only laid down after the primary cell wall growth is complete - in mature, non-growing cells, xylem elements - found between plasma membrane and primary cell wall - much thicker than the primary cell wall strength comes from lignin: a macromolecule of aromatic alcohol (phenol) monomers - high molecular weight - insoluble - impervious to water - rigid - 25% of dry weight of wood attributable to lignin - waste product of wood processing

Plant Breeding and Biotechnology

In the Dutch Elm Disease example I said that a few "resistant" strains had been developed.... but how? There has to be an exchange of genetic information, right? You want to "lose" the disease susceptibility but keep all of the other characteristics. There are two methods of achieving just that: Plant breeding: developing genetically different offspring via multiple generations of sexual propagation - physically placing the pollen onto the stigma. This is a very, very slow way of doing things, but until a couple of decades ago it's all we had. Force pollination and fertilization, wait for seed production, germinate the seeds, grow the plants to the point where whatever desired trait (disease resistance, fruit taste/appearance, flower aroma/appearance, etc.) can be determined or tested. It took SOOOOO LOOOONG. Still does. Plant biotechnology: a.k.a. genetic engineering. GMOs have a very negative stigma, but hopefully the short mini lecture after this will help dispel some of the misinformation, answer any questions you might have, and explain why the vast majority of "genetically modified organisms" are worth having.

How does water travel through the whole plant once it's inside the root?

Instead of re-writing everything in this image... read the numbered boxes on this image for an explanation of how water move from the root through the stomata on the leaves (and also, why water that lands on a leaf can't just be sucked inside). You just learned about apoplastic and symplastic movement in the root, but that's actually one of the last steps because the forces driving water movement are evaporation, cohesion, and tension of the water.... and the evaporation happens at the leaf!

Nucleus and Rough ER

Location of DNA and some RNA

Meiosis vs. Mitosis

Meiosis is a type of cell division that reduces the total number of chromosomes by half, creating a gamete that can then be joined with another gamete in the process of sexual reproduction. This is how sperm and egg cells are created. Remember this because MY-OH-MY it's sexual in nature (meiosis - MY-OH-SIS - MY OH MY....get it?) Mitosis is a type of cell division that divides a cell once to create another completely identical cell, with the same number of chromosomes. This is how non-sexual cells like skin in humans and parenchyma in plants are created.

Monocots vs. Dicots

Monocots: - parallel veins - flowers come in multiples of 3 - fibrous root system Dicots: - netted veins - flower parts in multiples of 4 or 5 - taprooted root system

Passive transport can occur via channels

Net direction is based on electromechanical driving force and since it's electrochemical i.e. along the gradient, this is passive - aquaporins: water channels that are highly selective (no ions pass through). They supplement but do not replace diffusional transport of water across membranes

Nutrient mobility

Nutrients can move one of two directions in plants. Acropetal means towards the apex; transport up. Basipetal means towards the base, transport down. Nutrients can also be classified as either mobile or immobile. Mobile nutrients can be moved up or down - deficiency symptoms of mobile nutrients appear on older (lower, larger) leaves first. Mobile nutrients are N, P, K, Mg, and S. Immobile nutrients can only move up, so deficiency symptoms appear on new leaves (smaller, higher up) first. Immobile nutrients are Ca, Fe, Zn, Mo, B, Cu, and Mn.

Water

On the first page I hinted that plant-water relations are dictated by the soil properties. Well, now that you've taken a crash course in physical soil properties (i.e. soil texture), we can talk about water. Oh, I should note - these rules about texture and water also apply to growing media. We just can't classify manufactured media into "clay, silt, and sand" because they are usually mostly organic, and are also usually trademarked blends. But the same rules apply with regards to large, medium, and small particles and their relationship to water. So first let's talk about the water cycle. This should be a review, so take a look at the fantastic graphic from the USGS below.

Soil Water Terminology

On the previous page you learned that gravitational water is the volume of water that drains within the first 24 hours... after that happens, the soil is at field capacity, that is, the amount of water a soil can hold against the pull of gravity. Once plants have pulled all of the available water from the soil, they risk drought stress. Wilting is the loss of plant turgidity due to excessive water loss - transpiration doesn't stop just because the roots cannot continue pulling water from the soil, so the plant begins to dry out. Incipient wilting is when a plant wilts, but recovers when placed in a saturated atmosphere (i.e., it rains again, or the relative humidity is 100%). This commonly happens with hydrangeas - they are very sensitive to heat and water stress; they'll often wilt during the hottest part of the day, and perk back up as it cools in the evening. Incipient wilting point is the soil moisture content (the volume of water in the soil) at which incipient wilting occurs. Permanent wilting is when a plant wilts but cannot recover when placed in a saturated atmosphere. You may have guessed that Permanent wilting point is the soil moisture content at which permanent wilting occurs. There is not a defined permanent wilting point because it varies so greatly between soil types and species. Some agronomists back in the 1950s decided that 1500 kPa pressure would define permanent wilting point, but the problem is that, first - 1500 kPa varies wildly in percent moisture content across various soil types and second - some plants have been proven to pull water out of soil beyond 1500 kPa (my dissertation actually did that). So... permanent wilting point is a term thrown around now pretty often but nobody knows what it really means, because it is entirely dependent on the soil type and plant being discussed!

Plant clones and Ramifications

One of the biggest benefits to vegetation plant propagation is the resultant uniformity. Whether that means all of your fruit trees are ready to harvest at the same time or all of your azalea shrubs are blooming simultaneously, uniformity is the name of the game.... except when it comes to diseases. Allow me to tell you the story of Dutch Elm Disease. The American elm tree was formerly one of the greatest street trees in America; they grew tall and had beautiful vase-shaped canopies that created a nice visual frame when planted down either side of a street. The disease was introduced to the US in 1928 and isolated in New York until the forties, when war demands led to a decrease in quarantine procedures. Long story short, by 1989 over 75% of the American elm trees in the United States had perished. Some surviving trees are diseased but being treated, and massive efforts have led to the hybridization of resistant strains, but there have still not been any truly immune trees. This is a worst-case scenario, but it paints a vivid picture of the flip side of vegetative propagation and cloning: if disease or pest is introduced, the entire population of plants can be wiped out before advances in sciences can develop a cure or treatment.

Plant Pigments

Pigments are chemical compounds that reflect only certain wavelengths of visible light. Chlorophyll is a pigment, and you already know it appears green. But plants aren't only green, so you may have correctly assumed that there are other pigments as well. Refer to the image below as we walk through a couple of the other major plant pigments (there are others, but I'm not going to make you learn all of them). Carotenoids are plant pigments that, among other things, function as photoprotectants (they protect plants from UV damage). Examples of carotenoids are carotenes (found in carrots) and xanthophylls (found in leaves). When carotenoids are present in leaves, they are usually masked by chlorophyll until the seasons change. Carotenoids range in color from yellows to oranges to reds, but it's easy for me to remember carotenoid starts out like "carrot", and so it's yellow-orange. Flavonoids have gotten a LOT of attention in the major media in recent years because they are powerful antioxidants. Diets rich in antioxidants and flavonoids have been linked to cancer prevention; whether that's true or not, there's no arguing that flavonoids are good plant nutrients. Some of the more well-known flavonoids are anthocyanins (blueberries are a rich source). Flavonoids range from yellow to red to blue to purple - they can be almost any color because they are so diverse, but for this course remember them as red, purple, or blue. You probably noticed I have leaves pictured next to the carotenoids AND the flavonoids, but didn't mention the leaves in my written example of flavonoids. That's because flavonoids aren't always in the leaves like carotenoids and chlorphylls.

Defenses against cold stress

Plant evolutionary responses to cold may be less obvious than those against heat, but they are there. The primary example is dormancy. Fossil records tell us that early flowering plants were tropicals - they didn't go dormant over winter because they didn't need to. As plants evolved, they developed the ability to go dormant during the winter... let's use tulips as an example. Tulips are an herbaceous (non-woody) flowering plant that sprouts in the spring and dies back in the fall. During the dormant season, the bulb is left in the ground. The bulb is a modified storage organ - the four primary parts of the plant are there, inside the bulb. Even in the winter. The developing flower and developing leaves are inside, waiting for winter to come and go, so that they can sprout. Bulbs are fleshy and full of carbohydrates - the carbohydrates are stored there while the leaves are photosynthesizing during the growing season, so that it has enough energy to survive winter and sprout in the Spring. This is an example of a physical plant response to cold that evolved over time.

Defenses against heat stress

Plants have evolved several defenses against heat stress, just as CAM photosynthesis evolved as a defense against water loss. Some plants have thick, wax-coated leaves. If you've ever seen a magnolia leaf or Chinese holly, you know those leaves are stiffer than, say, grass leaves. The thick waxy cuticle prevents excess water loss and guards against UV damage. On a cellular level, the chloroplasts in plant cells are always in motion to prevent UV damage. Don't believe me? There's a short video in the Unit 6 Additional Resources folder that shows chloroplasts moving in live plant cells! Some plants have white (i.e. highly reflective to UV radiation) leaves, or white hairs (called pubescence) on their foliage to avoid soaking up too much of the sun's radiant heat energy.A great example is Dusty Miller, a flower you may be familiar with and is pictured below:

Asexual Propagation

Plants undergo sexual reproduction, but they also undergo asexual reproduction. As the name implies, asexual reproduction is reproduction without sex, meaning no sperm, no egg, no transfer of genetic information to a whole new organism. This is possible because plant cells are totipotent: that means each individual plant cell has the potential to create a whole new, genetically identical, organism. If human cells were totipotent, we could clone humans by cutting off, say, an arm. The arm would then grow the rest of the body, and would be an exact genetic replica of the original person. Moreover, the original human who lost an arm in the name of cloning would also grow a whole new arm! So why on earth would a plant need totipotency? Think about the major challenge that most plants face: they are rooted into a single location, for better or worse. That doesn't exactly bode well for the proliferation of new generations, does it? So at some point plants developed the ability to reproduce genetic clones from pieces of themselves. This increases the probability of future generations succeeding, and also helps encourage the spreading of those generations to a new location.

stem anatomy: monocot

Primary Growth: The vascular bundles are randomly scattered in the ground tissue (usually comprised of parenchyma cells). Each vascular bundle is surrounded by a bundle sheath and contains xylem orientated towards the inside and phloem towards the outside of the stem. The outer layer is epidermis.

stem anatomy: Herbaceous or Young Woody Dicot or Gymnosperm Stem

Primary Growth: Vascular bundles are arranged as a ring between the cortex and pith. The pith and cortex are usually comprised of parenchyma cells. Inside each vascular bundle, the phloem is orientated towards the outside and xylem towards the inside of the stem. The outer surface is covered by the epidermis.

root anatomy: primary growth

Primary Growth: Root anatomy is virtually the same for monocots, dicots and gymnosperms. The vascular tissue occurs in the center, which is surrounded by two rings of cells, the pericycle and endodermis, then the cortex and epidermis. The cell walls of the endodermis that are perpendicular to the root surface (i.e. the radial and anticlinal walls) are sealed by a suberized band called the Casparian strip. Root hairs are extensions of the epidermal cells.

The Greenhouse Effect

Radiation from the sun is short wavelength radiation. About 10% is ultraviolet (recall the light spectrum - ultraviolet is just below the visible portion on the blue end), 40% is visible, and about 50% is short wavelength infrared (that's beyond the visible spectrum on the red end). When the short wave radiation is absorbed by the earth or objects on the earth, it is converted into heat energy and the objects' temperatures increase. They'll begin cooling themselves by conduction, convection, and radiation... releasing the heat energy. That re-emitted radiation is now long wavelength infrared. The atmosphere is opaque to long wave radiation. In the atmosphere, carbon dioxide and water absorb long wave radiation, which is then radiated back down, and the cycle continues. That trapped radiation just keeps bouncing around because it cannot get out. That is the greenhouse effect.

Light Quality

Rainbows are the result of light scattering through water droplets. The water acts as a prism - it reflects, refracts, and disperses visible light into its separate wavelengths. The image below details the light spectrum. The numbers across the top refer to the wavelengths of light in nanometers. That should be familiar to you, since you learned Photosystem 2 harvests photons at 680 nanometer wavelengths and Photosystem 1 harvests photons at 700 nanometer wavelengths. If you look at the bottom of the top row, you'll see short wavelengths on the left and long wavelengths on the right. The rainbow in the top box that is magnified into the bottom box is the portion of light that is visible. But wait; we can't see light - we see better in the light, but we certainly can't see it... can we? Actually, when you color, you are seeing reflected light. The reason plants are green is because they photosynthesize in the red and blue portions of the visible light spectrum, and all of the green light is reflected! So that red shirt you're wearing is simply reflecting red light. Light quality is a less complicated way of saying "spectral composition and distribution"... basically, light quality refers to where on the light spectrum that particular wavelength of light falls. In relation to plans, we will almost always be talking about the visible light spectrum - A.K.A. the color.

What does red light do to plants?

Red light is responsible for making plants flower and produce fruit. It's also essential to a plant's early life for seed germination, root growth, and bulb development.

Other functions for rubisco

Remember our old friend rubisco, the very important enzyme that harvests CO2 to start the dark reactions? Jeopardy fun fact: rubisco is the most abundant enzyme on earth. That's how important it is. It does so much more than just harvest carbon for plants. It also binds to oxygen. When rubisco binds to oxygen, the chemical pathway of the dark reactions gets very convoluted... one of the byproducts of the mess is carbon dioxide... perfect! We can just start the dark reactions over again! Except the plant expended valuable energy creating the very product it could have initially harvested. It is the opposite of photosynthesis - a plant harvested oxygen to yield carbon dioxide instead of harvesting carbon dioxide to yield oxygen! That "backwards photosynthesis" is called photorespiration and is detrimental to plants. If a plant starts using its ATP and NADPH inefficiently - harvesting oxygen instead of carbon dioxide - they will eventually be using more energy on photorespiration than on photosynthesis... they'll be using sugar instead of making sugar. It's the plant version of a diet, really - scientists have done experiments forcing plants into photorespiration, while the plants sit on a balanced scale... and over time, the total weight of the plant decreased! So how can plants prevent this?

Net Chemical Reaction for Aerobic Respiration

Respiration is the process by which plants break down glucose and convert its chemical energy to a useful form (i.e., ATP). Below is the balanced chemical equation for plant aerobic respiration: C6H12O6 + 6O2 + 6H2O → 6CO2 + 12H2O + ENERGY(ATP) [one mole of glucose yields a whopping 36 molecules of ATP!] Wait wait wait. You've been taught your whole life that plants use carbon dioxide and give off oxygen and that's why we love plants and plants love us, right? Well, yes... but plants need oxygen also (see chemical reaction above).

So long chloroplast, hello mitochondrion!

Respiration takes place in the mitochondrion (plural mitochondria) of the cell, just like in animal cells. You can think of mitochondria as the power plants of the cell; just the way a nuclear power plant harnesses nuclear energy and converts it to a usable form, the mitochondria harness the chemical energy of sugar and convert its to a form that plants can use. By now you should be able to guess that the "usable" energy (I like to think of it as energy currency) in plant cells is ATP

Hybrids

Result from a cross of two organisms that are genetically different - interspecific: aka mules (donkeys and horses are both from the genus Equus) - intergeneric: Leyland Cypress (cross between Cupressus macrocarpa and Chamaecyparis nootkatensis) - two different genera (genus)

stem anatomy: Woody Dicot or Gymnosperm Stem

Secondary Growth: Remnants of the pith occur in the center, surrounded by rings of xylem (one ring for every year), then the cambium. The phloem is ridged (dilated). Rays transverse the xylem and extend into the phloem (where they dilate). The outer surface is covered by the periderm or bark, which occurs as irregular layers.

Illustration of plant demonstrating the major defiicencies

See diagram

Nutrient Functions

See diagram

Organs and Tissue Systems in Plants

See diagram

Sexual Reproduction

Sexual reproduction requires a sperm and an egg. Reach way back to high school biology and recall that the sperm and egg cells contain only half of the genetic information required; putting the two halves together yields a whole organism. There are several implications of sexual reproduction: Sexual reproduction results in a an organism that is genetically different than both parents (it contains genes from both parents, but is not identical to either parent) Sexual cells (the sperm and egg) undergo meiosis; that's sexual cell division in which the amount of genetic information is split in half, to prepare to be joined with another half Pollination AND fertilization must both occur for successful sexual reproduction. Pollination: the transfer of a pollen grain to the stigma of a flower Fertilization: the union of a sperm cell and an egg cell

Cryptochrome

So far we've talked about red (photosynthesis and phytochrome), orange (carotenoids), yellow (xanthophylls), and green (plants reflect green light). So that leaves the blue region. Enter cryptochrome. [Are y'all too old for the kids' show Tales of the Crypt Keeper? Because I think of the crypt keeper every time I think of cryptochrome.] Anyway... Cryptochrome is a photo receptor that is sensitive to blue light. It is involved in circadian rhythms, but also in phototropism. Yes, that's another bolded word. Don't hate me. Know how sunflowers track the sun during the day, or how house plants will begin to lean towards the window? That's phototropism - directional growth towards a light source. Cryptochrome is the gate keeper for that mechanism.

Light Quality and Type of Growth

So if "light quality" refers to the "color" of the light, or more specifically the wavelength of light along the visible light spectrum, we can assume that various qualities of light will affect plant growth differently.... and we would be right! In general (because there are ALWAYS exceptions to every rule!), blue light (wavelengths around 450 nanometers) will favor vegetative growth while red light (wavelengths above 650 nanometers) will favor reproductive growth. There is a TON of information out there about this, because of certain high-value not-entirely-federally-legal crop production. That crop production is fully dependent on reproductive growth, so folks know a lot about how to force that growth. I'm not going to go into that any further, lest I get a warning message on my work computer that I'm venturing into "flagged" internet browsing territory... but feel free to delve into that. I urge you to consider Dr. King's medicinals course if you're interested in that particular arena. :) In short though, when the ratios of the visible spectrum striking a leaf are manipulated to favor blue or red, you can get vegetative vs. reproductive growth, respectively! And focus on the "manipulated" part - it's nearly if not completely impossible to manipulate natural sunlight in this fashion, so when considering manipulating growth through light quality, we are almost always talking about artificial light, and these days that pretty much means LEDs. P.S. I remember this because "R"ed and "R"eproductive start with the same letter!

Sand, Silt, and Clay

Soil texture is determined by the ratio of large, medium, and small particles: Sand (Large): 0.05-2mm diameter particles. It is large; individual particles are visible with the naked eye. It is chemically inert and offers little in terms of soil chemistry. Silt 0.002-0.05mm diameter particles. Silt is in the middle in size and chemical properties of sand and clay. Clay <0.002mm diameter particles. Clay highly complex structurally, and is negatively charged, contributing to soil chemistry. When wet clays are sticky and viscous; when dry they shrink and crack. The soil texture triangle categorizes different soil textures based on their ratios of sand, silt, and clay.

Soil Functions

Soils provide water and nutrient uptake, gas exchange, and anchorage for plants. In this unit soils refers to mineral or field soil, the outer weathered layer of the earth's crust or growing media, manufactured or synthetic "potting soils". Field soils applies to plants growing in the field, or directly in the earth. Growing media applies generally to container-grown plants, although field soils can be amended with growing media. Regardless, the functions of s oils remain the same.

Scarification and Stratification

Some plant species require seed scarification to overcome quiescence from a hard seed coat. Scarification is the weakening, opening, or altering the coat of a seed or husk to encourage germination. It can happen in several ways: Mechanical scarification is physically damaging or altering the seed coat to speed up germination. Bluebonnet seeds have a hard seed coat that require mechanical scarification; they can be nicked with a knife or rubbed with sandpaper. Chemical scarification uses chemicals, usually through soaking, to promote germination. Sulfuric acid or even household bleach can be used, depending on the species. Serotiny is a requirement for heat in order to release seeds. A great example is the Jack Pine (cones pictured below) - the pine cone remains closed by thick resin unless it is heated enough to melt the resin in order to release the seeds. This is just one reason that controlled burns are necessary for good forest management - some species just won't release their seeds to allow germination without fire. [If this interests you, there's a YouTube video by University of Wyoming Extension linked in the Unit 6 Additional Resources] Some plant seeds don't need to be scarified to germinate, but do require a period of cold. This is especially true for plant species native to the temperate climate zone; how else will the seed "know" when winter is over? Stratification is a period of cold storage (32-45 F) for 6-12 weeks to overcome embryo rest.

Other Plant Organ Dormancies

Stratification and scarification relate specifically to seed dormancies, but other plant organs can experience dormancy as well: Vegetative and Flower Bud Dormancy Cold is required for some species to flower or start growing vegetatively in the spring, especially temperate species. Chilling requirement is the number of hours of cold temperatures between 32-45 F. This is especially common in fruit trees such as cherries, peaches, plums, and apples. Peach cultivars, for example, are classified by their chilling requirement - it doesn't matter how great a peach cultivar is if it's not planted in the right climate. Too many chilling hours and it will flower too soon and risk frost damage. Too few chilling hours and it will flower too late, and the fruit won't have a chance to set. Check out the Unit 6 Additional Resources for a map of chilling hour zones in the US. Flowering Bulb Dormancy This is the tulip example from a few pages ago - flowering bulb species (tulips, lilies, amaryllis, etc.) all have a chilling requirement in order begin vegetative growth in the spring.

Is a potato a stem or a root?

Sweet potato - stores carbohydrates - grows underground - will not turn green when exposed to light - requires part of the root cap in order to be used propagatively - a root White potato - stores carbohydrates - grows underground - Will turn green when exposed to light - Requires a bud to be used propagatively - a stem

tissue culture

Technique for growing pieces of living tissue in artificial media

Temperature and heat

Temperature is a qualitative measure of the amount of heat energy; the measure of the intensity or degree of heat energy. Heat is a quantitative measure of the amount of heat energy and can be measured various ways: calorie: amount of heat required to raise 1g water by 1 degree C Kilocalorie (Kcal or in America, Calorie capitalized, as is listed on food): 1000 calories British Thermal Unit (BTU): amount of heat required to raise 1lb water by 1 degree F specific heat: the amount of heat (calories) needed to raise 1g of a substance by 1 degree C (water = 1.0 There are three ways to transfer heat energy Conduction: flow of heat energy through a medium from molecule to molecule. Convection: mass movement of heat energy Radiation: flow of energy as electromagnetic waves, with no transferring medium. When radiation is absorbed it may be converted to heat energy.

apomixis

The ability of some plant species to reproduce asexually through seeds without fertilization by a male gamete. - an exception to the rule of nonclonal embryony - ex: citrus and crabapples, or the formation of bulbils in garlic

C4 Metabolism Review

The first modification in the C4 metabolic pathway is that instead of rubisco, the enzyme that harvests carbon dioxide is PEPcase (PEP carboxylase, or phosphoenolpyruvate carboxylase - see why I called it PEPcase?). So PEPcase fixes CO2, but instead of splitting the product into a pair of 3-C sugar acids, the product is malate, a 4-carbon acid that travels to the bundle sheath cells. You can see those identified in the illustration below. The graphic below is showing an illustration of a leaf if you cut a piece of the leaf out and then zoomed in on the cut edges, for both C3 and C4 plants, where the vascular bundles are the leaf veins, and everything else is the tissue and cells around them. C3 and C4 plants have bundle sheath cells - those are the cells that are bundled around the vascular tissue; but the arrangement of the mesophyll cells in C4 plants is a little more organized. There is mesophyll entirely surrounding the bundle sheath cells in the C4 leaf, which creates a physical barrier between the bundle sheath and the stoma. The stoma is open, allowing CO2 and the evil oxygen molecules into the leaf. So not only do we not have RUBISCO performing the carbon fixation, we've added a physical barrier between the oxygen and the dark reactions. In both C3 and C4 plants, the stoma open during the day, and close at night. That may sound like a no-brainer; the dark reactions depend on the products of the light reactions, so you would want all of the photosynthetic processes happening at the same time!

chemiosmotic model

The mechanical energy provided by the flow of H+ ions is stored as chemical energy in the ATP bond.

Low Temperature Extremes

The minimum cardinal temperature for plant growth is 40-50 F for most plant species; the minimum for survival varies greatly by species, but is generally categorized as follows: tender or chilling sensitive (i.e. tropicals, houseplants): 32-45 F semi-hardy: 15-29 F hardy plants: less than 0 F Cold stress is more likely to occur in microclimates, or small areas with a climate different than the surrounding area. An example of a microclimate would be the north side of a building, or a north-facing slope. At our latitude, north-facing slopes are more shaded, because the equator (and the sun) are to the south year-round. Freeze damage can occur even without a frost. If temperatures are low enough to cause freeze damage but the relative humidity is low, then frost will not form although plant cells have frozen. Regarding cold damage, it isn't the cold itself that damages plant tissues; rather it is the ice. Water expands as it freezes, so as water-filled plant tissues freeze, the cells rupture.

Manipulating Growth with Nutrient Ratios

The nutrient ratio is the relative proportion of N to P2O5 to K2O in a single fertilizer. This ratio can be manipulated to favor vegetative (shoots, leaves) over reproductive (fruit and flower) and underground storage (root, bulb, etc.) growth. To favor vegetative growth, use a high N, low P and K fertilizer; a 2-1-1 or 3-1-1 ratio fertilizer. An example of those fertilizer analyses might be 10-0-0 or 24-6-12 (which is actually a 4-1-2 ratio, but still has a higher proportion of N, which is the goal). To favor root, underground storage, or reproductive growth, you need a low N to high P and/or K ratio; a 1-2-2 or 1-3-2 fertilizer would work. Examples of those analyses might be 8-16-24 or 8-24-16.

Soil pH and Plant Nutrition

The orange bars indicate the "optimal" soil pH, at which most nutrients are available, even though some would be more available at a higher or lower pH. The actual pH value is listed across the bottom, with descriptions of the pH across the top.

dermal tissue system

The outer protective covering of plants. - function: protection made up of two tissues: - epidermis: a single cell layer thick on herbaceous plant parts - periderm or bark: corky tissue that replaces the epidermis in woody plants

Soil Chemistry

The previous page alluded to soil chemistry when we were comparing clay, silt, and sand particles. Specifically it refers to Cation Exchange Capacity (CEC) and pH. Cation Exchange Capacity (CEC) is a measure of a soil's capacity to exchange cations. Cations are positively charge particles; i.e., cations are plant nutrients. The higher the CEC, the more fertile the soil. The unit of measure is "milliequivalents per 100g dry soil or meq/100g". Bet you can't say that three times fast. Don't worry about the weird unit - I'd rather you focus on be able to define CEC as opposed to memorizing the unit of measure. pH is the negative log of the concentration of hydrogen ions... it's a measure of the acidity of a solution. pH ranges from 1 to 14; below 7 is acidic and above 7 is basic, while 7 is neutral. In a later unit you'll learn how pH directly affects plant nutrition, but for now don't worry about it.

genetic engineering

The process by which humans induce or change DNA, RNA, or proteins in an organism to express a new trait or change the expression of an existing trait - done on a molecular level

How does water get into the roots?

When water enters the root, there are two different paths it can take. Apoplastic movement happens through the apoplast. The apoplast is just free space outside the cell's plasma membrane - all of the different cells' plasma membrane create a continuous apoplast, so it's a very nice way for water to move. I remember apoplastic movement occurs around the plant cell because both words start with the letter A! Symplastic movement happens via the symplast. The symplast is a continuous network of the cells' protoplasts - basically all of the "guts" of the different plant cells are connected to the guts of all of the other plant cells via ports in the cell walls and plasma membranes. The ports are called plasmodesmata. The network of ports and guts is called the symplast. I remember symplastic movement occurs straight through the cell because both start with the letter S! Here's the kicker: while water can enter the root either way, once the water hits the Casparian Strip it HAS to travel symplastically. The casparian strip is a waxy zone around the interior of the root that prevents the root from drying out. It basically allows water to go into the xylem, but prevents water from going back out. The apoplast doesn't cross the casparian strip; if it did, water could flow out of the plant just as easily as it flows in. Check out this diagram demonstrating apoplastic and symplastic movement.

Phototropism

When you learn about plant hormones in Unit 9 you'll learn about auxin, which is the plant hormone that controls phototropism; however, auxin is responsible for so many different plant growth responses that it's easier to introduce phototropism now. The image below shows how phototropism works: 1 - Auxin is represented by the red dots in the tip of the stem; you may remember back in Unit 2 when you learned stem morphology, the bud at the tip of a growing stem is called the terminal bud. That's where auxin is produced. As sunlight strikes the terminal bud, auxin is produced, encouraging growth towards the sun. 2 - As the sun moves across the sky, the cells on the shaded side produce even more auxin, because those shaded cells want more sunlight. This production of auxin results in more elongated cells. 3 - Now, the cells on the shaded side are literally longer than the cells on the sunny side. This cell elongation continues, making the tilt towards the sun even more pronounced 4 - Auxin is now concentrated on the shaded side of the plant, bending the plant towards the sun.

Root anatomy: secondary growth

Woody Dicot or Gymnosperm Root - Secondary Growth: A woody dicot or gymnosperm root in secondary growth looks almost identical to a stem in secondary growth. Therefore, see Woody Dicot or Gymnosperm - Secondary Growth. The only difference is that the woody root has remnants of the xylem in the center as opposed to pith.

So when do you water your plants?

You can determine whether or not you should water a plant based on the soil, based on the plant, or through an empirical formula. Based on the soil You can either feel the soil, and learn through experience when you should water (best for house plants), or measure the actual water potential in the soil using one of a multitude of instruments. This is typically done in labs, or in agricultural production in which irrigation timing is based on the soil moisture. Based on the plant You can go by experience - if the plant starts to look a little wilted, water it; or by measuring the plant water potential with a device called a pressure bomb. Based on empirical formula Several empirical formulas to predict evapotranspiration rates (in mm/day) are available. Most formulas require soil moisture, relative humidity, wind speed and direction, solar radiation values, and crop information because transpiration rates vary so greatly between species. This is largely done in lab settings and in irrigation timing.

Plant Available Water

You just learned that plants draw water out of the soil until or unless there isn't enough water left to break the pressure differential; that is, until the negative pressure in the soil is more negative than the negative pressure at the leaf surface. But that sort of implies that a plant can die of drought while water still remains in the soil. And that's true. I'm going to reference the image below while defining "plant available water". Note the bottom X axis shows pressure in kilo pascals as "soil water suction"; here it's a positive measurement, because it's from the perspective of the soil (how positively the soil is pulling against the water). The top X axis shows the volumetric water content of the soil, as a percent. The further to the left, the more water in the soil and the lower the pressure. The further to the right, the less water in the soil and the greater the pressure. Chemically combined water is water found in the soil that occurs as a shell around molecules and compounds in the soil. Plants can't utilize this. The compounds hold the water more tightly than the pull of tension from the leaves. That's represented in the image by the section called "unavailable dry"... there's still measurable water in the soil, but it is not available to the plants. Hygroscopic water is water adsorbed onto soil particles. Some of this water is available to some species of plants - this water is right on the line between the "unavailable dry" and the "plant available water", right around 1500 kPa. Gravitational water is water that is held in large pore spaces of the soil immediately after rain or irrigating. It's the water that drains away in the first 24 hours following a rain or irrigation event. Some of that is utilized by the plants, but only until it freely drains away. That's what's shown in the far right of the image, under "unavailable drainage". Most of that water drains away before the plants really get ahold of it. Capillary water is water held by smaller pores via capillary action. Capillary action is why if you stick a straw into a glass of water, the water climbs up into the straw. If you use a narrower straw (i.e., a stir stick), the water climbs higher than a regular drinking straw because the diameter is smaller and thus there is greater capillary action. Capillary action works because of that whole cohesion thing that water molecules like to do. Try it! This is what's usually known as "plant available water"... between 15 kPa and 1500 kPa in the image below. The water held by larger pores is more readily available (smaller pressures, closer to 15 kPa) than the water held more tightly by smaller pores (still available water, but closer to the 1500 kPa) Now you should understand how soil texture (or, more specifically, the size of soil particles) directly determines plant-water relationships. If a soil or media has too many large particles like sand at the beach, the water will drain before the plant can use it. If there are too many small particles, like the heavy clays here in College Station, the soil holds so much water that the plant can't uptake enough before the oxygen is depleted, and then the roots rot. Remember that discussion a couple of units ago when you had to guess what would happen if you set a potted plant into a bucket of water and left it? That's an extreme example, but that's what would happen.

Meristem

a region of plant tissue, found chiefly at the growing tips of roots and shoots and in the cambium, consisting of actively dividing cells forming new tissue.

Leaf Morphology: leaf arrangements

alternate - one leaf attached per node, usually staggered (spiral) along stem. opposite - two leaves (a pair) attached per node, usually opposite each other. whorled - three or more leaves attached per node, usually equally spaced around the node.

apoplast vs symplast

apoplast: system consisting of cell walls through which water moves freely; including cells of dead vascular tissues such as xylem - if flows through cell wall: apoplastic movement symplast: continuum of protoplasts of many cells, together with the plasmodesmata which connect them - if flows through plasmodesmata: symplastic movement

Plant Nomenclature

assignment of names utilizing a formal system - common names vary across time and space - botanical names: scientific

Stem Morphology

bud - an underdeveloped and unelongated stem composed of a short axis with compressed internodes, a meristematic apex, and primordial leaves and/or flowers. terminal bud - a bud at the tip of a stem responsible for terminal growth. axillary bud or lateral bud - buds along side the axis of a stem; they were produced by the terminal bud during growth; once they grow out and form a lateral stem they become terminal buds of the lateral branch. flower bud - a bud containing a floral meristem which develops into flowers; usually larger than vegetative buds. leaf scar - a scar marking the former point of attachment of a leaf or petiole to the stem. internode - the part of the stem between nodes node - part of stem marking the point of attachment of leaves, flowers, fruits, buds and other stems. lenticel - rough areas on stems (and some fruits, ex. apple) composed of loosely packed cells extending from the cortex through the ruptured epidermis; serve as "breathing pores" for gas exchange. Only occur on young stems. growth rings - bud scale scars from the last terminal bud; they denote flushes of growth (usually per year). Can be used to age stems because usually 1 set of growth rings is produced per year on temperate trees in the Temperate Climatic Zone.

plant cell organelles

cell wall, chloroplasts, large central vacuole

Flower types

complete - contains all floral parts, i.e. sepal, petal, stamen and pistil incomplete - lacks one or more of the floral parts perfect - contains both pistil and stamen (may or may not have sepal or petal) imperfect - lacks either pistil or stamen (may or may not have sepal or petal) pistillate (female) - contains only pistil (may or may not have sepal or petal) staminate (male) - contains only stamen (may or may not have sepal or petal) sterile - both stamen and pistil are absent, or are non-functional

stem function

conduction of water, nutrients, hormones, and sugars - physical support - modified stems can provide carbohydrate storage and propagation

plant tissue systems

dermal, ground, vascular

Sun Leaves versus Shade Leaves

differences in light quantity affects plants as well Sun Leaves Thicker blades, smaller leaf area Multiple layers of palisade cells (to protect against UV damage) Less chlorophyll Chloroplasts segregate along the sides of cells and shade each other High PS in high light Shade Leaves Thinner blades, larger leaf area Single layer of palisade cells More chlorophyll Chloroplasts near surface of leaf, no shading PS better in low light In this image, the sun leaves are on top - they are smaller, because they can receive adequate light for photosynthesis without stretching out. The shade leaves from the inside of the canopy are pictured on the bottom. The shape is the same, but the shade leaves are much larger, because they have to have more surface area to receive enough light for photosynthesis! Next time you're outside, take a look at the leaves deep within the canopy of a shrub versus the leaves around the outside of the shrub's canopy... there are likely some differences in shape and size, and maybe even color.

Hormone production and translocation

each of the five hormones are identified according to where they are produced on the left. On the right, all of the parts of the plant are noted, and the various ways each part may be affected by hormones is noted.

All flowering plants (angiosperms) can be classified as...

either monocots or dicots

Plant hormones

endogenous organic compounds active at very low concentrations, produced in one tissue and translocated to another place in the plant where their effects on growth and development are manifested - endogenic: formed or occurring in a system - translocation: movement from one place to another

Plasmodesmata

function: channels through cell walls that connect the symplast (the soup everything floats in) of two cells - channels lined with plasmamembrane - Impart cell to cell communication via desmotubule

Smooth and Rough Endoplasmic Reticulum

function: communication across the cytoplasm

Golgi apparatus

function: membrane and polysaccharide synthesis

Turf

grasses for lawns, landscapes, sport facilities and golf courses (in Agronomy in many Universities)

layering (vegetative propagation)

inducing roots on an intact (or nearly so) plant) - air layering: interrupt cambium and cover wound with moistened medium to force root development (works well with rubber plants) - simple layering: low hanging branch covered with soil with or without wounding (many shrubs do this) - tip layering: tips of plants develop roots where they touch the soil (blackberries and raspberries) - mound layering: soil mounded to cover base of specially pruned young trees (apple rootstocks)

apical dominance

inhibition of lateral buds by the apical meristem - varies with plant species (vines strong, shrubs weak) - varies with plant age (younger = stronger apical dominance) - decreases in basipetal direction - readily altered by pruning or chemical treatment

Leaf Morphology: compound leaf

leaflet - secondary leaf of a compound leaf. rachis - an extension of the petiole bearing leaflets. petiolule - the leaflet stalk. petiole - the leaf stalk. stipules - leaf-like appendages (at the base of the petiole of some leaves).

energy transfer

light is one of the ways in which energy is transferred. 1) conduction - molecule to molecule 2) convection - mass movement 3) radiation - radiant energy transferred as electromagnetic waves light - light is the layman's term for visible radiant energy in the 400 to 700 nm wavelength region of the spectrum. In other words, it is the form of radiant energy (i.e. radiation) that animals can see. It is also the wavelengths of radiant energy that plants use in photosynthesis and for most other reactions that require light.

Specialized structures used for propagation

modified stems - bulbs - corms - tubers - rhizomes - pseudobulbs - runners modified roots - tuberous roots

Plant Types Based on Flower Type Present

monoecious - both staminate (male) and pistillate (female) flowers occur on the same plant; ex. corn, cucumber dioecious - staminate (male) and pistillate (female) flowers occur on separate plants; ex. holly, persimmon, ginkgo

plant

multicellular eukaryote living organism whose cell walls are rigid capable of producing its own food through photosynthesis - Eukaryote cells have a membrane-bound nucleus and organelles: plants, animals, fungi

3 Basic Cell Types in Plant tissue

parenchyma, collenchyma, and scelerenchyma

active vs passive transport

passive transport: along a chemical or electrical gradient - require a difference in ion concentration on each of the two sides of the membrane, or a channel - two types: via electrochemical gradients (i.e. chemiosmosis) or via channels active transport: against a chemical or electrical gradient - requires carriers - ion concentration difference represents a source of free energy - two types: via symporters and via antiporters

phytochrome

plant pigment responsible for photoperiodism plants contain a photoreceptor (a pigment that detects and receives light from certain wavelengths) - phytochrome - that is sensitive to light in the red and far red region of the visible light spectrum. Red light has a wavelength of roughly 620-740 nanometers; far red light has a wavelength of roughly 710-850 nanometers. Even though far red is technically inside the visible spectrum (not quite infrared but close), it is only visible to some eyes, and only dimly so. Phytochrome is used by many angiosperms to regulate the time of flowering based on day length - photoperiodism. It also regulates seed germination along with a few other processes. It exists in two forms in plants - Pr (r for red) and Pfr (fr for far red). Phytochrome is reversible, which means it can switch back and forth between the Pr and Pfr form, depending on the quality of light it has detected. Exposure to red light converts phytochrome to the functional, active form (Pfr), while darkness or exposure to far-red light converts it to the inactive form (Pr). It may sound backwards - that the active form is Pfr - but think of it as active and waiting for the opposite signal to turn it off, which would be far red.

sexual propagation basics

pollination: transfer of pollen to the stigma fertilization: joining of a sperm cell with an egg cell (requires pollination first) Ploidy: the number of sets of chromosomes in the nucleus of a typical cell (humans have 23 sets of chromosomes in pairs of 2) haploid: 1N = half the number of expected chromosomes (sexual cells are typically this) diploid: 2N = 2 of each chromosome (nonsexual cells usually this) sexual = by seeds propagation by seeds is sexual reproduction because the seed is the result of fertilization benefits: - seeds are widely available and inexpensive - large scale agriculture dependent on seed production - seeds may have complex dormancies that impede germination until a certain set of environmental characteristics are met

primary cell wall structure

polysaccharide - cellulose: chain of sugars - Hemicellulose: filler between cellulose microfibrils - Pectin: cementing agent

Leaf function

primary photosynthesis organ (sugar creation) - carb or water storage - modified leaves can be used for protection (thorns) or support (tendrils on a vine)

primary cell wall function

protection, structural support, enzymatic

sclerenchyma cells

protects seeds and support the plants 2 Types: a) fiber b) sclereid or stone cell - evenly thickened, lignified (tough) secondary cell walls - dead at maturity - support in mature tissue - examples: fiber - bamboo cane sclereid - seed coat stone cell - pear fruit

collenchyma cells

provide flexible and mechanical support; found in stems and leaves - unevenly thickened, non-lignified primary cell walls - support in growing tissues - example: strings in celery stalks - longer than wide

Vegetative vs. Reproductive organs

reproductive: flower vegetative: roots, stems, and leaves

4 major parts of a plant

roots, stems, leaves, and flowers

Plant Taxonomy

science of naming and classifying plants

Anatomy of Gymnosperm leaf (pine needle)

see diagram

Monocots vs. Dicots: stem anatomy

see diagram

Parts of a flower

see diagram

anatomy of a dicot leaf

see diagram

plant classification system

see diagram

Twig anatomy

see image

2 methods of propagation

sexual: requires fertilization (the joining of sperm and an egg) asexual: does not require fertilization; based on the concept of plant cell totipotency

Chloroplast

site of photosynthesis in plant cells

Gibberellins (GA)

site of synthesis: shoot and root meristems, embryos in seeds growth response: - cell elongation and expansion - stimulation of alpha-amylase activity - elongation of flower stalks of chilled buds - reversal of physiological dwarfism commercial uses of gibberellin inhibitors: - height control in flowering potted plants - height control in bedding plants commercial uses of GA actives: - increase flower size in certain ornamentals - increase berry separation and size in bunch grapes - overcome shallow dormancies in vegetative buds - stimulate seed germination, especially in beer production, so that all of the seeds have uniform germination when going into the brew

Auxin

site of synthesis: apical and root meristems, young leaves, seeds in developing fruit growth response: - cell elongation and expansion - suppression of lateral bud growth - stimulation of abscission (detachment) in young fruit or delay of abscission - hormone-impacted tropisms commercial uses: - stimulation of adventitious roots - herbacide for dicots (2,4-D) - fruit thinning or fruit holding - sprout prevention or encouragement in pruning (function of apical dominance)

Ethylene

site of synthesis: many plant tissues - gaseuous and autocatalytic (stimulates its own production) - production stimulated during fruit ripening, physical stress (wind storms), senescence, mechanical damage, or infection growth response: - encourage senescence and death of tissues - fruit ripening - strengthens supportive tissues in woody plants commercial uses: - flower initiation in bromeliads and pineapples - forcing fruit ripening (bananas, tomatoes) - degreening citrus - abscission induction prior to mechanical harvest (cherries) commercial uses of ethylene inhibition: - achieved by chemically scrubbing the air - long term storage of apples - treatment of cut flowers with silver thiosulfate to increase shelf life delayed ripening of tomatoes to increase shelf life

Cytokinin

site of synthesis: root meristems, young leaves, fruits and seeds growth response: - cell division - stimulates adventitious bud formation - delays senescence - promotes some stages of root development commercial uses: - axillary bud development in orchids and lillies - antioxidant in cut salads to prevent browning - fruit size stimulator when mixed with GAs

abscisic acid (ABA)

site of synthesis: stressed leaves, dormant seeds, dormant buds growth response: - stomatal closure - inhibits germination of some seeds - inhibits active growth of lateral buds

Limitations of hybrids

something has to be given for the hybrid to exist - mules are sterile

Secondary cell wall function

strength, support, protection

Active transport carrier types

symporter: both molecules flow in the same direction - usually bring solutes into the cytoplasm, either from the extracellular medium or an intracellular compartment (i.e. an organelle like the vacuole) antiporter: molecules flow in the opposite direction

Anatomy

the formation, development, and presence of structures of an organism (inside)

morphology

the physical form or shape of biological structures, and relationships of those structures to each other (outside)

propagation

the process of creating a new plant from any of a variety of sources: seeds, cuttings, bulbs, and other plant parts

grafting and budding (vegetative propagation)

the vascular cambium can regenerate vascular connections - graft scion (the top, desirable plant) onto the rootstock (the bottom, root portion of plant) why? in fruit trees, it is common that rootstock plants are less susceptible to soil-borne illnesses while good scion plants produce more desirable fruits, so grafting is a way to join them

parenchyma cells

thin, non-lignified primary cell walls - filler, storage, protection, photosynthesis - isodiametric - examples: flesh of potato, lettuce leaf

Leaf Morphology: simple leaf

tip - the terminal point of the leaf blade or lamina - the flattened, green, expanded portion of a leaf. margin - edge of a leaf. midrib - the most prominent central vein in a leaf. lateral veins - secondary veins in a leaf. petiole - the leaf stalk (connects blade to stem). stipules - leaf-like appendages (at the base of petiole of some leaves).

ground tissue system

tissues that are neither dermal nor vascular function: depends on type of tissue Tissues: a) cortex - outer region of stems and roots. b) pith - center of stems. c) mesophyll - middle of leaves and flower petals.

Root function

water uptake, nutrient uptake, anchoring, physical support, modified roots can provide carbohydrate storage or be used for propagation

Research and development pipeline

work to: - drought and cold tolerance - disease resistance - insect resistance - multiple herbicide tolerance - improved product quality/nutrition