-shade- inc:stem & leaf elongation, apical dominance, shoot:root ratio; dec: leaf mass per area, defenses -phytochromes transduce red & far red light->auxin->expansins->elongation->shade avoidance -far red liaht/dark-Pr conformation will cause PINs to mainlv be on the sides of cells in the plant stem-most Auxin will flow to the sides & accumulate in stem-inc. Auxin accumulation in stem will cause a higher cell elongation rate & inc stem length -red light/bright-Pfr conformation-PINS channels on the bottoms_of cells in the stem causing Auxin flow down towards the roots- lower elongation rate of the stem -Pfr absorbs far-red light-transforms pigment to Pr, inhibiting JA defense pathway -inc. pH-dec. elongation, dec. expansin activity, same solute potential in symplast- dec [H+]/more basic in apoplast, less role for expansins, less gradient of [H+] into cell, less Cl- influx -kinase blocker-dec elong, dec expansin, less neg solute potential- proton pumps not activated, transport of H+ from symplast to apoplast declines -[auxin] in plant cell-in:auxin transport in through AUXes(H+ pump activity); out: auxin diffusion PIN([Auxin] gradient & # of PINs) -apoplast-high [Na+]-solute potential low-harder to lower solute potential inside leaf cells enough to bring water in- dec cell elongation & make leaves smaller -Iarge leaves in shade: shade = low R:FR-> high Pr:Pfr->Pr signal cascade->PINs move to sides of cells->auxin accumulates in leaves -auxin enable expansins->enable elongation->more auxin, more elongation -H2O-atm to xylem:water potential gradient between atm & internal leaf air space->water flux from air space to atm through stomatal pores->dec. in waiver potential in air space-> inc. in evaporation of H2O from mesophyll cell walls-> dec. in radii of water menisci around cell wall fibers->inc. water surface tension from cohesion-> tension(neg. pressure) in water column->lifts H2O through leaf apoplast from xylem in roots -H2O enters roots through osmosis -guard cell open-1)phototropins(PHOT) absorb blue light and autophosphorylate 2)activated phototropins phosphorylate BLUS1 3) BLUS1 signaling regulates protein phosphatase 4) protein regulates activity of a protein kinase 5) kinase promotes binding of a protein to H- ATPase, stabilizing the proton pump in the active state 6) membrane hyperpolarization drives K+ in & CI- enter via H+/CI- cotransporter 7) dec in H2O potential drives water uptake & stomata
opening -guard cell close-ABA binds to ABA receptor-signal cascade that stops proton pump-opens CI- channels: Cl- leaves down electrochem grad- membrane depolarizes-V-K+ channels open: K+ out- [solute] dec, inc solute potential- H2O leaves via osmosis, dec pressure potential-cells shrink, pores close -regulation-close/flaccid: ion out (inc solute pot), water out, dec pressure potential// open/turgid ions in(dec solute pot), water in, inc pressure pot -inc heat-dec h2o in LAS->inc water pot gradient btw LAS & air->evaporation of h2o from menisci-> dec radii of menisci w/ more adhesion of h2o to cell wall fibers-> tension inc (dec pressure pot) in mensici->ince press pot btw menisci & xylem in stem-> inc water flux from xylem to menisci, inc rate of h2o uptake -cavitation-large magnitude neg pressures force liquids into gas phase-leads to desiccation & cell death-breaks cohesion-water not carried in part of plant
-high transpiration rate- low resistance