BIOL 172 c35b-38&32/33

pulling of xylem sap

*transpiration cohesion cell sap (water/mineral solution in xylem) 1) evaporation of water from leaf creates negative water pressure in leaves. 2) water film pulled into cell wall pores lowers water potential 3) water pulled through symplast and apoplast of mesophyll 4) water from xylem replaces lost water

Three transport routes for water and solutes

1) apoplastic route through cell walls and extracellular spaces. 2) symplastic route, where water and solutes cross a plasma membrane once and then travel through the cytosol. 3) transmembrane route, where water and solutes repeatedly cross plasma membranes as they pass from cell to cell.

stomata closes from drought

K+ exits guard cells closing during day or due to water deficiency due to production of abscisic acid in roots and leaves.

ammonification

NH₃ produced by decay

land plants acquire resources form both above and below ground

algal ancestors of land plants absorbed water, minerals, and CO2 directly from the surrounding water. evolution of xylem and phloem in land plants made possible the long-distance transport of water, minerals, and products of photosynthesis. adaptions in each species represent compromises between enhancing photosynthesis and minimizing water loss.

Crassulacean Acid Metabolism (CAM)

adaptation for photosynthesis in arid conditions. plant takes up CO2 and incorporates it into a variety of organic acids at night; during the day, CO2 is released from organic acids for use in the Calvin cycle.

leaf orientation

affects light absorption. in low-light conditions, horizontal leaves capture more sunlight. in sunny conditions, vertical leaves are less damaged by sun and allow light to reach lower leaves.

development of soybean root nodule

along a legume's roots are nodules composed of plant cells "infected" by Rhizobium bacteria. inside the root nodule, Rhizobium assumes a form called bacteriods (contained within vesicles formed by the root cell). plant obtains fixed nitrogen from Rhizobium and Rhizobium obtains sugar and an anaerobic environment.

genetic engineering can improve plant nutrition and fertilizer usage

aluminum in acidic soils damages roots and greatly reduces crop yields. introduction of bacterial genes into plant genomes can cause plants to secrete citric acid and that bind to and tie up aluminum.

what are the two major transport pathways through plants?

apoplast consists of everything external to the plasma membrane (includes cell walls, extracellular spaces and the interior of dead cells such as vessel elements and tracheids). symplast consists of the cytosol of all living cells in the plant, as well as the plasmodesmata.

apical dominance

axillary buds are kept dormant by chemical suppression from the apical bud. if the shoot tip is removed or shaded, the axillary buds are released from this apical dominance. lateral shoots emerge from axillary buds that have been released from dormancy.

how solutes and pressure affect water potential

both solute concentration and pressure affect water potential in plants, as expressed by the water potential equation. solute potential (ψS, aka osmotic potential) of a solution is directly proportional to its molarity.

cation exchange

cations are displaced from soil particles by other cations, particularly H+. Displaced cations enter the soil solution and can be taken up by plant roots. negatively charged ions do not bind with soil particles and can be lost from the soil by leaching.

guard cell function

cells buckle and open when turgid close when flaccid K+ uptake lowers guard cell water potential water diffuses into guard cells from surrounding epidermal cells

stomata opens from internal clock

circadian rhythm

annuals

complete life cycle in one year

topsoil

consists of mineral particles, living organisms, and humus

soil solution

consists of water and dissolved minerals in the pores between soil particles. after a heavy rainfall, water drains from the larger spaces in the soil, but smaller spaces retain water because of its attraction to clay and other particles.

irrigation

huge drain on water resources when used for farming in arid regions (75%). primary source of irrigation water is from aquifers (underground water reserves). depleting of aquifers can result in subsidence (settling or sinking of land). irrigation can lead to salization (concentration of salts in soil as water evaporates). drip irrigation requires less water and reduces salinization.

soil conservation and sustainable agriculture

in contrast with natural ecosystems, agriculture depletes the mineral content of soil, taxes water reserves, and encourages erosion.

stomata closes from high temperature

increases CO2 in mesophyll due to respiration

smart plants

inform the grower of nutrient deficiency before damage has occurred.

endodermis

innermost layer of the cortex. regulates passage of substances from the soil into the vascular cylinder. surrounds the vascular cylinder and is the last checkpoint for selective passage of minerals from the cortex into the vascular tissue.

stele

innermost primary meristem is the procambium, it gives rise to the central vascular cylinder. vascular cylinder has a solid core of xylem and phloem surrounded by a cell layer called pericycle.

flowers & pollinators

insects help angiosperms to reproduce sexually with physically distant members of their own species. most angiosperms lure insects with nectar or pollen; both plant and pollinator benefit. mutualistic associations are common between plants and other species. humans are mutualists that consume parts of crop plants and in return provide plants with water, nutrients, protection, and seed dispersal.

root pressure - pushing

ions pumped into stele osmatic uptake of water creates pressure, particularly at night. can't keep up with transpiration can only push water a few meters. guttations (exudation of water) hydrathodes

phytoremediation

land unfit for agriculture because contamination of soil or groundwater with toxic pollutants. biological, nondestructive technology that reclaims contaminated areas. plants capable of extracting soil pollutants are grown and are then disposed of safely. ex: Alpine Pennycress: removes and stores zinc at 300x greater than most plants.

rhizosphere

layer of soil bound to the plant's roots has high microbial activity because of sugars, amino acids, and organic acids secreted by roots.

stomata opens from light

light induces K+ uptake - blue light receptors stimulate proton pumps - photosynthesis in guard cells produces ATP for H+ pumps

perennials

live for many years

protoplast

living part of the cell, which also include the plasma membrane.

endomycorrhizae (arbuscular maycorrhizae)

microscopic fungi hyphae extend into the root. these mycorrhizae penetrate the cell wall but not the plasma membrane to form branched arbuscules within root cells. 85% of plants.

humans have used artificial selection and genetic engineering to

modify wild angiosperms into modern crop species.

loams

most fertile topsoils and contain equal amounts of sand, silt, and clay.

nutrient uptake in plants

most plants take up CO2 from the air through the shoot system and water and nutrients from the soil through roots. some plants that live in nutrient poor soils use carnivory to obtain mineral nutrients.

absorption of water and minerals by root cells

most water and mineral absorption occurs near root tips, where the epidermis is permeable to water and root hairs are located. root hairs account for much of the surface area of roots. after soil solution enters the roots, the extensive surface area of cortical cell membranes enhances the uptake of water and selected minerals

mycorrhizae

mutualistic association of fungi and roots. fungus benefits from a steady supply of sugar from the host plant. host plant benefits because the fungus increases the surface area for water uptake and mineral absroption. mycorrizal relationships are common and might have helped plants first colonize land.

ectomycorrhizae

mycelium of the fungus forms a dense sheath over the surface of the root. these hyphae form a network in the apoplast, but do not penetrate the root cells.

water and mineral uptake

mycorrhizae (roots and the hyphae of soil fungi form mutualistic associations). mycorrhizal fungi increases the surface area for absorbing water and minerals, especially phosphate. mutualism with fungi helped plants colonize land.

nitrogen fixation

nitrogen fixing bacteria reduce N₂ to NH₃ using nitrogenase (enzyme)

conservation: sustainable agriculture

nutrients (organic and inorganic fertilizers) adjusting pH irrigation erosion control phytoremediation

plasmolysis

occurs when the protoplast shrinks and pulls away from the cell wall.

stomata regulators

opening: light, CO2 concentration, internal clock closing: drought, high temperatures and wind

short-transport of water across plasma membranes

osmosis: diffusion of water into or out of a cell that is affected by solute concentration and pressure. water potential: physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.

pressure potential (ψP)

physical pressure on a solution. pressure potential can be positive or negative. ex: solution drawn up by a syringe is under negative pressure; when expelled that is positive pressure.

transport

plant cells use the energy of H+ gradients and membrane potential to cotransport other solutes by active transport. plant cell membranes have ion channels that allow only certain ions to pass. diffusion, active transport, and bulk flow act together to transport resources throughout the plant. plants move large volumes of water form their roots to shoots every day.

parasitic plants

plant that derives some or all of its nutritional requirement from another living plant.

soil contains a living, complex ecosystem

plants obtain most of their water and minerals from the upper layers of soil. living organisms play an important role in these soil layers. basic physical properties of soil: texture and composition

macronutrients

plants require nine of the essential elements in relatively large amounts: carbon oxygen hydrogen nitrogen phosphorus sulfur potassium calcium magnesium

short-distance transport of solutes across plasma membranes

plasma membrane permeability controls short-distance movement of substances. both active and passive transport occur in plants. in plants, membrane potential is established through pumping H+ by proton pumps. in animals, membrane potential is established through pumping Na+ by sodium-potassium pumps.

turgor pressure

positive pressure exerted by the plasma membrane against the cell wall and the cell wall against the protoplast.

primary tissues from apical meristem

primary growth of roots produces the epidermis, ground tissue, and vascular tissue. protoderm is the outermost primary meristem; gives rise to the epidermis. root hairs: epidermal cells modified for absorption, make up 70-90% of the total root surface area.

nitrifying bacteria

produce nitrite (NO₂⁻) and nitrate (NO₃⁻) in soil/water by oxidizing ammonium (NH₄⁺).

leaf area index

ratio of upper leaf surface of plant divided by the surface area of land on which it grows. higher than 7 results in shading to the point that self-pruning occurs.

denitrifying bacteria

reduce nitrate (NO₃⁻) to N₂

biennials

require two growing seasons

growth of the root tip

root tip is covered by a root cap, which protects the apical meristem as the root pushes through soil. growth occurs just behind the root tip in three zones of cells: - zone of cell division - zone of elongation - zone of maturation

soil texture: soil particles are classified by size; from the largest to smallest

sand, silt, and clay.

ground meristem

sandwiched between the protoderm and procambium, gives rise to the ground tissue. ground tissue, mostly parenchyma cells, fills the cortex, the region between the vascular cyclinder and epidermis.

soil structure

sandy soils don't retain enough water to support plant growth; clay soils retain too much. most fertile topsoils typically have pores containing about half water and half air. soil's composition refers to its inorganic (mineral) and organic chemical component.

hydrathodes

secretion of water, among loose parenchyma located at the end of small veins in a leaf

xerophytes and transpiration

small thick leaves leaf color pubescence (dermal hair development) thick cuticle stomata of underside of leaf shed leaves in dry season store water in stems prostrate growth rosette leaves Crassulacean Acid Metabolism (CAM)

Root Architecture and Acquisition of Water and Minerals

soil contains resources mined by the root system. root growth can adjust to local conditions. ex: roots branch extensively into high nitrate pockets and straight through low nitrate pockets. roots are less competitive with others roots from the same plant than with roots from different plants.

soil horizons

soil is stratified into layers O horizon: leaves, stems, other organic material A horizon: topsoil contains organic matter, broken down rock, and humus B horizon: much less organic matter, much less weathered C horizon: composed mostly of partially weathered rock, serves as parent material for upper layers.

adjusting soil pH

soil pH affects cation exchange and the chemical form of minerals. cations are more available in slightly acidic soil, as H+ ions displace mineral cations from clay particles.

fertilization

soils can become depleted of nutrients as plants and the nutrients they contain are harvested. fertilization replaces mineral nutrients that have been lost from the soil. commercial fertilizers are enriched in nitrogen, phosphorus, and potassium. organic fertilizers are composed of manure, fishmeal, or compost.

Shoot Architecture and Light Capture

stems serve as conduits for water and nutrients and as supporting structures for leaves. phyllotaxy (arrangement of leaves on a stem) is specific to each species. most angiosperms have alternate phyllotaxy with leaves arranged in spiral. angle between leaves is 137.5°; likely minimizes shading of lower leaves.

photosynthesis - water loss compromise

stomatal pores are necessary to allow diffusion of CO2 into the photosynthetic tissues of leaves. over 90% of the water lost by plants is evaporation from stomatal plants. shoot adaptions represent compromises between enhancing photosynthesis and minimizing water loss.

transport within plant tissues

symplast: by the cytoplasm apoplast: by cell walls/middle lamella long distance transport by bulk flow movement due to pressure differences: - transpiration tension - xylem - hydrostatic pressure - phloem

bulk flow

the movement of a fluid driven by a pressure gradient enhanced by the structural adaptions of xylem and phloem cells. - mature tracheids and vessel elements have no cytoplasm and seive-tube elements have few organelles in their cytoplasm. - perforation plates connect vessel elements and porous sieve plates connect sieve-tube elements.

plants convert nitrate (NO₃⁻)

to ammonium (NH₄⁺)

leaf area

total area of the leafy portions of all plants in a community affects the productivity of each plant. self-pruning (shedding of lower shaded leaves) occurs when they respire more than photosynthesize. light absorption is affected by the leaf area index...when higher than 7, shading has reached point of self-pruning.

phloem loading and unloading

translocation sieve tube member/sieve plate directional flow source (sucrose loading) sink (sucrose unloading) transfer cells H+ pump: creates potential for sucrose cotransport pressure flow: 1 m/hr loading end: high solute concentration in phloem, due to loading - hydrostatic pressure greatest at loading end unloading end: high solute concentration outside phloem, due to unloading

aquaporins

transport proteins in the cell membrane that allow the passage of water. the opening and closing of aquaporins affect the rate of osmatic water movement across the membrane.

sustainable agriculture

using farming methods that are conservation minded, environmentally safe, and profitable.

most monocot stems

vascular bundles are scattered throughout the ground tissue, rather than forming a ring.

most eudicot stem anatomy

vascular tissue consists of vascular bundles arranged in a ring.

Casparian strip

water can cross the cortex via the symplast or apoplast. the waxy Casparian strip of endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder. water and minerals in the apoplast must cross the plasma membrane of an endodermal cell to enter the vascular cylinder.

water movement across plant cell membranes

water potential affects uptake and loss of water by plant cells. if a flaccid cell is placed in an environment with a higher solute concentration, the cell will lose water and undergo plasmolysis.

inorganic components

• Cations (for example K+, Ca2+, Mg2+) adhere to negatively charged soil particles; this prevents them from leaching out of the soil through percolating groundwater. • Negatively charged ions do not bind with soil particles and can be lost from the soil by leaching.

organic components

• Humus builds a crumbly soil that retains water but is still porous. - Increases the soil's capacity to exchange cations and serves as a reservoir of mineral nutrients. • Topsoil contains bacteria, fungi, algae, other protists, insects, earthworms, nematodes, and plant roots. - These organisms help to decompose organic material and mix the soil.

controlling erosion

• Topsoil from thousands of acres of farmland is lost to water and wind erosion each year in the United States • Erosion of soil causes loss of nutrients. erosion can be reduced by - planting trees as windbreaks - terracing hillside crops - cultivating in a contour pattern - practicing no-till agriculture

cohesion and adhesion

H bonding cohesion maintains a column of water adhesion to xylem walls problem: cavitation (vapor pocket) solution: refilled by root pressure or pit (detours) or secondary growth

plants and soil microbes have a mutualistic relationship

dead plants provides energy needed by soil dwelling microorganisms. secretions from living roots support a wide variety of microbes in the near root environment.

humus

decaying organic material

stomata opens from CO2 concentration

decrease in mesophyll CO2

endophytes and rhizobactera

depend on nutrients secreted by plant cells and, in return, help to enhance plant growth by: - producing antibiotics that protect roots from disease - absorbing toxic metals or increasing nutrient availability - converting nitrogen into forms usable by the plant. - producing chemicals that stimulate plant growth

symptoms of mineral deficiency

depend on the nutrient's function and mobility within the plant. deficiency of mobile nutrient usually affects older organs more than younger ones. deficiency of a less mobile nutrient usually affects younger organs more than older ones. most common deficiencies are those of nitrogen, potassium, and phosphorus.

water potential (ψ)

determines the direction of movement of water. water flows from regions of higher water potential to regions of lower water potential. potential refers to water's capacity to perform work. measured in megapascal (MPa, unit of pressure).

transport of xylem sap

effective delivery of water and minerals 15-45 meter/hour from xylem in roots to leaves transpiration (provides pulling force) upward flow of water and minerals

long-distance transport: the role of bulk flow

efficient long-distance transport of fluid requires bulk flow. water and solutes move together through tracheids and vessal elements of xylem and sieve-tube elements of phloem. branching veins in leaves ensure that all cells are within a few cells of the vascular tissue.

dicot root anatomy

epidermis, parenchyma cortex, and endodermis make up the cortex.

carnivorous plants

grow in bogs acid soils deficient in nitrogen and phosphorus, which is secured from prey produces food by photosynthesis

epiphytes

grows on another plant and obtains water and minerals from rain. do not tap into hosts for sustenance.

control of transpiration

guard cells photosynthesis-transpiration compromise: - need for water - gas exchange: CO2 and O2 - need to transport minerals to leaves - evaporative cooling

soil compaction

heavy equipment reduces pore space between soil particles. slows gas exchange and reduces root growth. prevented by reducing use of heavy equipment.