Bio 371 final

final

plants concentrate things that are present in ______ concentrations

low

macronutrients

essential in large quantities, c/h/o from air and water (not considered minerals), n/p/k/s/ca/mg are mineral nutrients available to plants through the soil as dissolved ions in water

micronutrients

essential in trace quantities, cu2+/cl-/ni2+

what are some of the essential elements? what do they do?

17 essential elements, components of nucleic acids (N,P) and amino acids (N,S), function as enzyme cofactors (Ca2+), role in photosynthesis (mg2+, fe2+, fe3+) or regulation of osmotic potential (K+)

nitrogen

abundant element in air, most limiting to plant, triple bond requires specific enzyme, nitrogen cycle provides soil nitrogen

nitrogen fixation

incorporates atmospheric n2 into plant-available compounds nh4+, completed by nitrogen fixing bacteria

bacterial ammonification

breaks decaying organic n compounds into nh4+, plants take up nh4+ but prefer no3-

bacterial nitrification

oxidizes nh4+ to no3-

why do plants convert no3- to nh4+?

to assimilate n into organic compounds

what relationship do legume (pea) root nodules have with nitrogen fixing bacteria?

symbiotic association

nitrogen depletion from soil

harvesting of crops removes all nutrients from he soil, early agriculture allowed land to replenish lost nitrogen through free living bacteria or symbiotic association with roots, increase in population led to continuous use of lands, depleted all nitrogen (which is essential)

how to improve nitrate content in soil?

crop rotation with legumes helps (but not sufficient), use of nitrate fertilizer tremendously increased yield during green revolution, plants grew taller and posed lodging problems, led to developing dwarf breeds of both rice and wheat (reducing a hormone required for stem elongation)

how to deal with tall, lodging prone plants?

plants grew way taller and posed lodging problems, researcher bred cereals (crossing with other cultivated varieties), led to developing dwarf breeds of both rice and wheat, this allowed the dwarf crop to produce more yield with fertilizers and had no lodging problems

what happens to excess fertilizer/nitrogen?

90% of nitrogen added to crop-lands are lost as surface runoffs and end up in rivers/lakes/oceans, causes algal blooms (eutrophication) which eventually sink to the bottom where bacteria feed on them leading to depletion of oxygen, leads to catastrophic consequences to animal life on the sea or lake floors, huge trade off: we benefit tremendously by applying nitrogen fertilizers but end up hurting the ecosystem due to run off

eutrophication

enrichment of an ecosystem with chemical nutrients such as compounds containing nitrogen and phosphorous

soil

living skin of the earth, contains soil-mineral particles, compounds, ions, decomposing organics, water, air, organisms

humus

decomposing organics, hold water and nutrients, negatively charged

what does the relative amount of soil particles determine?

soil properties (water and mineral availability)

what determines water availability in soil?

sandy soil is looser and holds less water than clay soils, humus increases water availability

soil solution

a combination of water and dissolved substances that coats soil particles and partially fills pore spaces, available for plant uptake after gravity drainage, water molecules are attracted by negatively charged clay and humus particles

clay is ______

alkaline (oH around 8, negative charge)

mineral deficiencies

minerals are taken up by the roots from the soil

chlorosis

yellowing of plant tissues due to lack of chlorophyll

mineral availability in soil

minerals are dissolved in water, can passively enter plant roots along with water, selectively absorbed by roots via ion-specific transport proteins, both cations (na+, ca2+, mg2+) and anions (no3-, so42-, po43-) are present in soil solution but not equally available to plants

mineral cations (mg2+, ca2+, k+) are _____ to negative soil particles

adsorbed

cation exchange

replaces mineral with H+ produced by roots as excreted H+ or carbonic acid (produced by respiring root cells)

what is true for availability of minerals in soils rich in clay with a pH of 8?

cations are tightly bound while anions can leach out easily

anions (no3-, so42-, po4-)

weakly bound to soil, move freely into root hairs, leach easily by excess water

soil is usually ______ with _______ charged ______ particles bound to _______. what happens to anions under these conditions?

alkaline, negatively, clay, cations, anions are readily available but can be leached out easily

what happens when soil turns acidic due to pollution (acid rain)?

negative charges on the clay are occupied by H+ and the cations are leached out easily and become unavailable to the plants

alkaline vs acidic soils

alkaline: anions leach out easily, acidic: cations leach out easily

passive transport

requires no metabolic energy, substance moves down a concentration or electrochemical gradient (membrane potential), simple diffusion (h2o, o2, co2 ex), transport proteins facilitate diffusion (ex ion channels and carrier proteins)

active transport

requires metabolic energy (atp), substance moves against gradient, transport proteins using energy (ex H+ pump)

what is the function of root hairs?

greatly increase root surface area, absorbs water and minerals

mycorrhizae

symbiotic association between fungus and plant roots, both partners benefit by two way exchange of nutrients, plant provides fungus with carbon, fungus increases plant's supply of soil nutrients; mainly mobilization of P (improve P-uptake by plants)

what is present on root cell plasma membrane?

membrane transporters (ex K+ channel)

what do charged particles require?

channel or transporters

what is the most important layer of soil?

top soil with humus

what are the ways plants can move water and solutes?

into and out of cells, laterally from cell to cell, over long distances from the root to shoot or vice versa

short distance transport in plants

into and between cells, to and from vascular tissues

long distance transport in plants

move substance between roots and shoot parts

osmosis

passive movement of water across a selectively permeable membrane

aquaporin proteins

allow rapid movement of water through hydrophobic membrane core

water potential

the potential energy of water, driving force, the total of its components (solutes and standard atmospheric pressure)

what is the water potential of pure water?

0 megapascals

water moves from _____ to ____ water potential

high, low

how do solutes affect water potential?

lower water potential (solutes are negative value), increase in solutes inside the cell will result in more negative solute potential and more positive turgor pressure inside the system, increase in solutes will increase pressure potential of the system

pressure potential

force required to stop movement, positive pressure increases water potential, negative pressure reduces water potential

plasmolysis

when plants lose more water than they gain, causes wilting

central vacuole

tonoplast membrane, maintains turgor pressure

tonoplast membrane

the membrane that surrounds the large vacuole

why do plant cells adjust solutes?

keep itself turgid and allow water to come in until equilibrium is reached

water follows the ______

solutes

what happens when more solutes are taken up into the vacuole?

reduced water potential inside the cell causing water to move into the vacuole, vacuolar expansion causing increased pressure until equilibrium is reached

increasing pressure in a water solution (with sucrose added) results in an _____ in water potential, and water potential in a system ______ under tension (negative pressure)

increase, decreases

where does water diffuse into?

roots in cell walls of root epidermal cells

apoplastic pathway

water (with dissolved minerals) moves across cortex to endodermis via cell walls and intercellular spaces until casparian striple

endodermis

innermost layer of the cortex in land plants

symplastic pathway

water (with dissolved minerals) flows from cytoplasm of one cell to the next via plasmodesmata

what are the pathways of water into roots?

apoplastic pathway, symplastic pathway, cell to cell movement

plasmodesmata

channels through cell walls that connect the cytoplasms of adjacent cells

apoplast vs symplast + which is faster?

apoplast: outside the plasma membrane

symplast: inside of the cell or in the cytosol inside of the plasma membrane

apoplastic is faster

how do nutrients move?

taken up from the soil along with water, move through both apoplast (passively uptaken by roots) and symplast pathway (passive/actively uptaken)

how do endodermal cells behave?

act as a selective barrier so ions are actively transported (atp) into xylem, differing from water transport

where do most nutrients enter inside cells?

vacuoles or cell cytoplasm

casparian strip

forces apoplastic water and nutrients to symplast (in root endodermis), ensures that all water and solutes pass through a plasma membrane in order to enter the vasculature, allowing plants to regulate the ions that pass into the vascular tissue, act as a selective batter for ions, restricts solutes from flowing back

transpiration

evaporation of water out of plants, greater than water used in growth and metabolism

cohesion-tension mechanism of water transport

evaporation from mesophyll walls, replacement by cohesion (H-bonded) water in xylem, tension + negative pressure gradient + adhesion of water to xylem walls adds to tension, pulling force due to transpiration, adhesion of water to walls of xylem

what helps resist the effect of negative pressure on the column in cohesion-tension mechanism?

lignin-secondary wall, weight of the column, adhesive forces in xylem

why is leaf anatomy the key to processes moving water upward in plants?

facilitate transportation, large volume of air space provides surface area for evaporation, thousands to millions of stomata, short cell distances to xylem: each square cm contains thousands of xylem veins

water evaporation from leaf increases _______

tension

root pressure

positive pressure in roots that forces xylem sap upward, occurs in high humidity or low light, moves water up short distances

guttation

when root pressure strong enough to force water out of leaf openings, water is pushed up and out of veins

translocation

long distance transport of substances via phloem, multi-directional (xylem is unidirectional)

what flows through sieve tubes?

phloem sap (water and organic compounds), contain more than just sugar, amino acids, organic acids, organic nitrogen compounds, hormones, and other signal molecules

what drives the flow of phloem sap?

differences in pressure between source and sink

source

any region of plant where organic substances are loaded into phloem (ex mature leaves)

sink

any region of plant where organic substances are unloaded from phloem (ex growing tissues and storage regions)

formation of sieve tubes

alive at maturity, undergo partial programmed cell death, to have a larger area for flow of sap: as sieve tubes mature, they lose their nucleus vacuoles and organelles; sieve plates are modified cell walls with plasma membrane lined pores, sieve tubes are connected to companion cells that play a life supporting role

phloem

sieve tubes + companion cells

phloem mother cell ---> ____ + ____

companion cell, sieve element

mechanism of sugar loading

both apoplastic and symplastic; similar to xylem, substances eventually have to get into the symplast of the sieve tube to be transported

what occurs after sugar/sucrose moves into cell walls of phloem cells?

transporter proteins actively transport sucrose into phloem (need for plasma membrane)

sucrose comes through smaller ______ into ______ cells, processed into larger ____ and through larger ______ transferred to _____, trapped in companion cells and ____ can't return

plasmodesmata, companion, sugars, plasmodesmata, phloem, phloem

sugar unloading is mostly _____

symplastic

in leaves, sucrose is _____ _____ into ____. what happens when more sucrose is loaded into sieve tubes?

actively loaded, phloem, low water potential

pressure flow mechanism

moves substances by bulk flow under pressure from sources to sinks, based on water potential gradients, load from source --> transport in sieve tube --> unload into sinks

what does influx of water cause in the sieve tubes?

increase in pressure

sap flows in ____ toward the ____ (lower pressure)

bulk, sink

____ is unloaded into sink cells, water flows back to the ____ through osmosis

sucrose, xylem

why gas exchange

need a supply of co2 for photosynthesis, need to dispose o2 as waste

leaves adaptation for gas exchange

gas exchange by simple diffusion, to maximize the rate of diffusion: short distance between cells and external environment, thin layered leaf, gas filled space within leaves, large leave area, gas exchange through stomata

stomata

an aperture on epidermis of a leaf (mostly lower epidermis), consist of two specialized cells: guard cells that surround a tiny pore (stoma)

what happens to the gases during photosynthesis?

co2 enters and o2 leaves the leaf through opening stomata, water vapour will exit the leaf along a diffusive gradient

controlling water loss

more than 90% of water moving into a leaf can be lost through transpiration, the cuticle-covered epidermis: reduces water loss from leaves and stems, limits co2 diffusion for photosynthesis; opening stomata: co2 is absorbed but water is lost, transpiration-photosynthesis compromise

transpiration-photosynthesis compromise

plants balance transpiration and gas exchange by opening and closing stomata as environmental conditions change, stomatal opening/closing controlled by actively transporting K+ into/out of guard cells, water follows K+ by osmosis, turgid: stomata open, flaccid: closed

physiology of stomata

responding to many signals, biological clock, stomata open to increase photosynthesis: increasing light (blue), decreasing co2 concentration in leaf; stomata close under water stress: abscisic acid is hormonal signal for closure, synthesized by roots, mesophyll cells take up ABA from xylem and release it

stomata movements

transpiration losses of water must be regulated to prevent rapid dessication, cuticle limits h2o loss but also prevents co2 uptake, water is always lost when stomata open for photosynthesis, stomata opening controlled by K+, water follows K+ by osmosis, turgid stomata open, flaccid closed