BISC 101 Lecture Notes - Lecture 13: Auxin, Signal Transduction, Abscission
14 Mar 2016
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Document Summary
A single hormone can affect many different tissues or processes (pleiotropy) Several hormones can affect the same response, hormones do not work independently. Transported in xylem, phloem, by diffusion or cytoplasmic streaming. Environmental information receptors (signal transduction, photoreceptors) hormone signal (e. g auxin) hormone receptor on target cells signal transduction (secondary messengers cell function. Auxin binds to auxin receptors (tir1, abp1) signal transduction. Increases number of proton pumps h+atpases in plasma membrane. 1: lowers ph activating expansin enzymes that unzip cell wall structure, h+ establishes electrochemical gradient (membrane potential) ion/solute uptake into cell; water follows by osmosis, turgor pressure increases expansion of loosened cell wall (cell get larger) Ethylene (gaseous, auxin control, leaf abscission: decreased auxin (older leaves) = increased ethylene sensitivity, weakens cell walls at base of leaf (abscission zone)(winds pulls leaf off) Positive phototropism: growth of plant tip towards light.
