EXAM 3

Auxins

"The Growth Hormone" (controls development of the plant) Produced in apical meristems Causes an irreversible increase in size/cell elongation Migrates away from the sun (Apical dominance, phototropism, gravitropism, thigmotropism)

Abscisic Acid

"The stress hormone" - dropping of leaves - believed that it caused the leaves to drop but it doesn't Induces dormancy of plant parts but not important in abscission Applied to nursery plants before shipping to maintain dormancy and prevent damage (don't want to grow until ready to use them) Induces stomatal closure under water stress (closing everything up can reduce stress) Summary: Inhibitory chemical - involved in maintaining dormancy of buds during winter, preventing seeds from germinating too early/closing stomates when a plant is under drought stress.

Cytokinins

"the juvenility hormone" Produced in areas of cell division (meristem/cambia) - developing roots, shoots, seeds, fruits Stimulates cell division and delays senescence

Ethylene

"the maturation hormone" - chemical C2H4 Generated in ripening and wounded tissues; promotes ripening and senescence (aging) Gas at room temp; diffuses through air to other plants Reduce respiration and aging to extend shelf life: CA storage, hypobaric storage (Avoid storing strong ethylene producers near sensitive plants)

Why did Mendel choose peas?

(1822-1884) Chose peas for ease of culture, short life cycle, variety (could introduce another variety into the system), ease of hybridization (big flowers), self-polinating

Gravitropism

(Function of Auxins) "gravity leaning" - growth (negatively/positively) towards or away from the Earth

Thigmotropism

(Function of Auxins) "growth pattern leaning in response to touch" (peas - terminal leaflet into tendril - when tendril touches something, it climbs up it - like a trellis)

Phototropism

(Function of Auxins) "light leaning" - looks like plant is leaning towards the light -to avoid lopsided appearance, give auxins

Apical Dominance

(Function of Auxins) Mostly tips/buds/apical meristem Remove apical dominance by auxins

Five major groups of plant hormones

(Target located on proteins) Auxins Gibberellins Cytokinins Abscisic Acid Ethelyne

Side Graft

(Tomato grafting method) - merge rootstock into scion and cut off root system of the other plant

Tube Graft

(Tomato grafting method) grafting on epicotyl of tomato seedling, cut is made longitudinally and edge of scion plant placed in it

Indoor seed germination

(annuals) -Containers -Cleanliness -Germination mix -Temperature -Water -Light -Problems including dampening off - can splash in through watering - fungal disease in potting mix/air -Transplant and grow on -Hardening off (acclimation) - tender plant gets more adapted to stress; very protected in an open space for 10 days to 3 weeks -Transplant to garden

Law of Segregation

(proposed by mendel) Allele pairs segregate during meiosis, and randomly reunite during fertilization Can observe this in a one-trait punnett square

Law of Independent Assortment

(proposed by mendel) Expression of traits are not necessarily inherited together (Could be on different chromosomes)

Synthetic Auxins are used routinely to induce specific plant reactions. What are some of these reactions?

- Rooting hormone promote rooting of difficult plant-to-root stem cuttings - Spray on tomatoes to increase number of fruits - Spray on young apple and olive fruits to cause some to drop - Spray on nursery trees after pruning to prevent sucker growth - Spray on apples/pears/citrus fruits nearing maturation, to prevent early drop - Spray on potato tubers in storage to prevent sprouting (prevents nodes from developing into branches) - 2,4-D (Auxin solution) herbicide kills broadleaved plants (dicots) but doesn't harm grasses (monocots) (used in lawns)

Synthetic Gibberellins are used to induce specific plant reactions. What are some of those reactions?

- Spray on seedless grapes to increase size of fruit and distance between fruits - Treat seeds to break seed dormancy by replacing some plants needs to for cold temperature to speed production - Spray on some crops in production of "standards" (some trees) by promoting uniform germination of many species

Ethylene is used to induce specific plant reactions. What are some of these reactions?

- Sprayed on to bananas, honeydews, tomatoes, after shipment to ripen them - Sprayed on to ripe citrus fruits to cause color development of rind - Applied to pineapple plants to promote flowering/fruiting - Used to intensify color of cranberries early - Used to ripen coffee berries uniformly - Used to promote abscission of cherries and walnuts "1 bad apple spoils the barrel" - because it is a gas that transfers from plant to plant easily

Asexual (Vegetative) Propagation

-Mitosis -Cloning - leads to uniformity -Possible because of TOTIPOTENCY and DEDIFFERENTIATE -Many methods possible; some plants can be propagated by more than one method

A few examples of specialized structures (for propagation)

1) Bulbs - produce bulbets TWO TYPES a) Scaly - separate leaves/cloves (lilies and garlic) b) Tunicate - leaf tissue surrounds it (onions, tulip, daffodil) 2) Corms - produce cormels - mostly stem tissue/ replaced every year 3) Tubers - (potatoes) stems with buds. Buds = new growth 4) Rhizomes - are horizontal stems so it's more of a stem cutting (ginger)

Why did Mendel succeed?

1) Careful planning of his crosses 2) Peas are self-fertile 3) Mendel counted everything and applied good math skills 4) Mendel chose, quite by chance, traits controlled by single genes

What are the overall steps to plant breeding?

1) Create variation 2) Select for variation and make crosses and grow resulting plants 3) Evaluate and cull 4) Repeat steps 2&3 as needed 5) Release germ plasm of new cultivar 6) Propagate 7) Distribute

Mendel's hybridization process -

1) Emasculate pea; pollinate it with pollen from another pea 2) Observe and record traits, and hypothesize reasons for observations 3) First experiment involved study of spherical vs. dented seeds a) F1 seeds were all spherical, but dented seeds appeared in F2 generation (only traits that dominated others were expressed in F1 generation) b) suggested that trait could skip a generation

How are natural ecosystems different from crop ecosystems?

1) Fate of carbon - carbon can become more available in wild, stay/recycle in wild, remove carbon in our crop systems 2) Progression of communities - natural system: progress from pioneer to climax communities, in Maine: things spread/grow quickly and get replaced by other species, grassland: shrubs to forest that can replenish itself (climax forest) -ag systems: always at pioneer stage/never allow progression - not as stable

What are the goals of plant breeding?

1) Increase the quality and yield of crops 2) Increase tolerance to environmental pressures 3) Incorporate resistance to diseases 4) Increase tolerance to insect pests 5) Increase tolerance to herbicides

Seven major biomes of the world

1) Rainforest - topical and temperate 2) Grassland (Savannah) 3) Shrubland (chaparral) 4) Desert 5) Temperate deciduous forest 6) Coniferous forest (taiga) 7) Tundra

DNA does four things in plant breeding. What are they?

1) Store genetic information 2) Copy genetic information for future generations of cells (duplicated during interphase) 3) Express genetic information 4) Sometimes change the genetic message, through mutation

Why graft in general?

1) perpetuate a clone 2) plant cuttings might not root 3) seed time to maturity 4) rootstock advantages 5) special effects Example: tomato - - inbreed depression - one tomato might be disease prone so you graft it to a disease resistant plant Example: apples - (all of our apples are grafted) - makes apples easier to harvest (dwarfing genes) - disease resistance

Germination process

1) seeds imbibe water 2) enzymes convert stored protein to AA; fats/starches to sugar 3) oxygen diffuses into cells; energy from cellular respiration supports growth 4) embryo produces new cells through mitosis, causing growth 5) radicle emerges downward to anchor plant and take in water 6) shoot grows upward, pulled by hypocotyl; the meristem is protected by this process [7) either monocot or dicot germination process] 8) When new plant photosynthesizes, germination is complete (seedling's true leaves photosynthesize)

Why is grafting both simple and hard?

1- scion/rootstock must be compatible (the more related the two plants are, the better the chance of survival for grafting i.e. - same species are very compatible) 2- choice of grafting method (some methods better on for different plants) 3- temp range for callus formation 4- timing during season (graft when sap flows - spring) 5- precision of technique (better you are, more effective it is) 6- follow-up care

Healing chamber

100% humidity (slowly acclimating plants to the outdoor climate)

F1 Hybrids

2 Parent lines (P) homozygous (true-breeding AA/aa) create heterozygous (Aa) F1 generations (dominant traits only show - all same ratio) Cull out anything that looks odd Heterosis/hybrid vigor Robust, desirable traits

What is a biome, how are biomes created?

A collection of ecosystems with similar climate, soil and plant composition Climate is the main influence on ecosystems Organisms can live in more than one biome

What are the disadvantages of F1 hybrids?

A lot of maintenance Inbreed depression - losing vigor Unpredictible traits (lose aggregation of traits) Costly New seed every year

What can we change in agricultural systems?

Agriculture requires more land than the space in which crops are actually grown 1) energy inputs 2) land use Is renewable energy the answer?

How are open pollinated and heirloom varieties produced?

Allow self/cross pollination within crop type, collect and store seeds

Synthetic use of Cytokinins are used to induce specific plant reactions. What are some of these reactions?

Applied to young plants to enhance growth and development Kinetin available to home gardeners; increases yields of some fruits/vegetables (Cytokinins/ethelyene work together to promote abscission of plant parts)

"T-Bud"

Budding method (roses) dormant bud is cut off and placed in T-Cut of scion match up vascular cambium and wrap so bud is sticking out & cut off any new stems only want rootstock growth on bottom only want scion growth on top

How are the plants that grow in specific biomes determined?

Climate: 1) Soil 2) Temperature - how far N/S (latitude), and how far up/down (altitude) 3) Moisture/wind

PGRs (Plant Growth Regulators)

Commercially important tools for plant management (in particular: florists) Functions vary: support vigorous growth, retard growth, cause new tissue development

What is an ecosystem?

Community of organisms in a physical environment (biome = physical environment) "organisms" - includes plants, animals, fungi, bacteria, etc. Ecosystems are not closed systems We can apply what we learn from natural ecosystems to our crop systems (competition, niches, resources) Biotic components: autotrophs and heteotrophs

What are the advantages of F1 hybrids?

Cross two inbred lines = heterosis/hybrid vigor Know what you're going to get Uniform seedling development Early More adapted to stress Disease resistance High yields

Outdoor seed germination

Direct seeding allows for less control over conditions Row covers and other temporary structures can provide some control

Epigeal vs. hypogeal germination

Epigeal: cotyledons mature above the soil surface (bean) Hypogeal: cotyledons mature below the soil surface (pea)

Germination in dicots

Example: bean Epigeal vs. hypogeal germination Taproot either dominates or develops into a spreading fibrous root system

Germination in monocots

Example: corn (small cotyledon filled with endosperm - energy source) Radicle is protected by coleorhiza: plumule is protected by coleoptile (root has to develop first to support the rest of the plant (if there is no water to support the top of the system, the plant dies) In some, cotyledon mergers; in others, cotyledon delivers nutrients to embryo Primary root is replaced by by adventitious root system at base of young stem

Climacteric Ethylene production in fruits

Examples: apple, banana, melons, apricot, tomato, avocado, mango During climacteric, they produce ethylene and their respiration rates rise (CO2) Climacteric peak marks the peak of edible ripeness, taste and texture

Trench Layering

Flexible stem put in trench, at each node buried, a new plant develops

Rainforest (tropical/temperate)

Frost-free, wet/dry cycle Tropical - lush growth, most successful and most diverse, thin soils Temperate - temperatures change from winter/summer

Non-climacteric Ethylene production in fruits

Fruits ripen without producing ethylene or rise of respiration rate Examples: oranges, citrus, grapes, strawberries Should be picked when ripe; they don't ripen much after harvest

"Whip & Tongue"

Grafting method angled cut - "tongue" - in rootstock prepare scion wood with same cut as rootstock and fit together (graft union) wrap and tie to prevent from drying out the cut

Three developmental processes

Growth Differentiation (cells become different from one another) Morphogenesis (beginning of plant part shapes) *Differentiation and Morphogenesis depend on exogenous and endogenous factors

Green Revolution Negative Impacts

High-yield hybrids require more fertilizer and irrigation Loss of many traditional strains of crops Populations rose Not all places benefited equally (not more productive/require more) EXAMPLE: 30k varieties of rice in India to only 10 now

Graft Incompatibility

If the scion/rootstock are incompatible, the scion dies quickly. Rootstock sends up vigorous suckers (stems that complete against desirable scion for water/nutrients) Somestimes, a scion topples in a windstorm years later because the graft fails

How are F1 hybrids developed?

Inbreeding (only one person can breed them - only one person owns it)

Desert

Largest biome

Mound Layering (Stool Layering)

Mound of soil (~1ft) over base of plant to develop new plants (apple root stocks)

How does temperature effect seed germination and seed growth?

Must be appropriate for metabolic process; varies by species Keep it cool, germinate at a warmer temp than plant grows Most crops germinate best at 68-86F Some seed germinate best with dinural (day/night) temperature fluctuations Germination temperature range vs. optimum germination temperature (seeds germinate at warm temperatures but like to grow cool if cool season crops)

Green Revolution: Who, What, Where, When

Norman Borlaug Wheat breeding/genetics Began in Mexico 1943 - 1970 Research, development, technology transfer.

Coniferous forest (taiga)

Northern climates dominated by conifers cool winters Second largest biome fewer species/diversity than in a temperate forest

What is the difference between Open-Pollinated and Heirloom varieties?

OP: uniform across generations, maintain identity, homozygous, through continual inbreeding, many are self-pollinated (pea, bean, lettuce, tomato) H: Old, self-pollinated, maintained for many years

How does oxygen effect seed germination and seed growth?

Oxygen supports cellular respiration which provides energy for cellular activities

Plants are central to the productivity of ecosystems. Why?

Plants capture/store energy needed to drive system, nutrient cycling 1) Support services - forming soil (plant roots penetrating through rocks) 2) Provisioning services - food, fuel, fiber, medicine, etc. 3) Regulating services - control floods, disease movement, CO2 regulation, regulate stability 4) Cultural services - beauty, spiritual, recreation, etc.

How do you get a successful graft union?

Plants must be closely related to have success (same species works best) Rootstock & scion must be correct size Have to be healthy Have to have clean surfaces/work spaces/hands

Gibberellins

Produced in meristems, immature seeds, young leaves Work with Auxin to stimulate cell division/elongation Speeds germination process Breaks seed dormancy

How does water effect seed germination and seed growth?

Seeds imbibe water; this initiates germination (resumption of growth of seed) Water enters the seed through the micropyle - Water causes the seed coat to burst - Too much water prevents access to oxygen, killing the developing embryo

Budding

Similar to grafting but with buds

Simple Layering

Similar to tip layering but you leave the tip and bend part of the plant further back to grow new plants

Green Revolution Positive Impacts

Some countries became self-sufficient in production of some crops More food could be produced on a limited land base to support larger populations

How does light effect seed germination and see growth?

Some seeds need light and some need darkness to germinate - Light may stimulate or inhibit or not influence germination (Depends on species) Examples: lettuce, sensitive plant (darkness) Red light most important for germination

Temperate deciduous forest

Southern Maine 4 seasons deciduous trees (less recycling than in grassland, storage in stems, rain)

Layering methods used by plant propagators

Tip layering, simple layering, trench layering, mound layering (stool layering), air layering (marcottage), serpentine layering (compound layering)

Heterotrophic

Until the new plant photosynthesizes, it is using food reserves (depends on sorted energy/doesn't make own food)

Shrubland (chaparral)

West Coasts - 30-40 degree latitude (Northern hemisphere) hot dry summer/ cool moist winter

Autotrophic

When photosynthesis is initiated, almost all plants are self-feeding (When germination is complete)

Germ-Line Cell Mutations

affect offspring

Totipotency

all cells carry genetic information to do all plant functions every living plant cell has the genetic code needed to reconstitute all plant parts/actions

Plant Breeding Definition

an application of genetics the science of improving the heredity of plants (pg. 250-260)

External factors of seed germination and early seedling growth

can stop plant from germinating 1) temperature 2) water 3) oxygen 4) light/darkness

Tundra

dominated by small organisms (coldest) Canada, Russia, Antarctica North of coniferous forests low growing plants permafrost soil frozen except at surface

Internal factors of seed germination and early seedling growth

genetic potential, energy stores, hormones, cell/tissue structures

Stem Cuttings

goal is for the stem to reproduce roots cuttings are normally 2-4inches in length also known as "slips" grow a callus (tissue formed from the wound) that differentiate and become the roots 1) Herbaceous plants - easiest/high success 2) Woody Plants a) softwood - 1st year of growth/tree or shrub cut in early summer. b) semi-hardwood - cut in midsummer and take current years wood c) hardwood - take dormant in midwinter/mature stems and place in a cold greenhouse

Grassland (savannah)

grasses dominate forbes (non-grass) North American grassland = prairie

Linked Genes

interfere with independent assortment (when two alleles are close on the same chromosome, the can cross over and become linked)

Somatic Cell Mutations

mutations may affect the individual, but are not passed to offspring (not necessarily important - affects the outside of plants)

Root Cuttings

normally herbaceous

Leaf Cuttings

normally herbaceous houseplants

Tissue culture

one form of micropropagation Cultured in a lab on agar plate Develops a callus - little stem grows up Cut off the callus and rooted to produce new plants Can be used to produce a clone or variation

Not all ecosystems are natural. What are some ecosystems that we develop?

parks, urban, greenhouses, landscapes, crops, pasture

Cuttings

piece of a plant is "cut off" and put in place w/ the environmental conditions that cause it to generate the missing parts (time varies from plant to plant) -Stem, leaf and roots -Stock plants - what you are cutting from

Factors in propagation success:

plant health, rooting hormones, environment, vigor, water, moist/humid temp, potting mix

Air Layering (marcottage)

produces one new plant by making a cut in the stem and wrapping it with something dark like peat moss & plastic every time it grows a new leaf, it loses an old one

Inbreed Depression

reduced biological fitness of a given population due to inbreeding (the ability to survive goes down)

Propagation

reproduction, or the increase of the number of individual plants (process by which species survive in the wild)

Layering methods used naturally

runners (strawberries), stolons, offsets (pineapple/banana), suckers (raspberry/pineapple), crown division (herbaceous perennials planed in flower gardens like shasta, asters or peonies)

Dedifferentiate

some mature plant cells can return to a meristematic condition/develop a new growing point to regenerate those missing parts

Layering (propagation)

stem that is going to regenerate new roots is left attached to the parent plant (example: strawberry runners)

Grafting

the joining of the stem (scion) of one plant to a rootstock of another -Some plants do it naturally like the American Elm

Tip Layering

tip of stem/root/flexible branched plant raspberry, blackberry long, arching tips grow new plants

Serpentine Layering (Compound Layering)

zig-zag plant through the soil (Like a compound version of simple layering)