Module 3 Week 2 Notes
Module 3 Week 2 Notes BIOL 1520 L
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This 4 page Class Notes was uploaded by Natalie Seman on Monday October 19, 2015. The Class Notes belongs to BIOL 1520 L at Georgia Institute of Technology taught by Dr. Green in Summer 2015. Since its upload, it has received 25 views. For similar materials see Intro to Organismal Biol in Biology at Georgia Institute of Technology.
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Date Created: 10/19/15
Module 3 Notes Lecture 56 Plant Info Processing 40 Hormones Concentration affects the amount of each transcription factor produced 0 Changes in transcription responsible for changes in gene expression Blue Light Phototropic Response Coleoptile modi ed leaf forms sheath protecting emerging shoots of grasses Phototropism directed movement in response to light 0 Plants will not bend if blue light is ltered out 39 Bending only occurs toward blue light source 39 Chlorophyll A B are primary photosynthetic pigments Absorb bluered o BlueLight Receptors 39 Blue light receptor is a pigment Membrane protein is phosphOIyIated in response to blue light Phototropin o Photoreceptor that detects blue light and initiates phototropic responses Gene called PHOTI o Encodes bluelight receptor in plants 39 photIm is a mutant that codes for a protein that cannot be phosphorylated plant fails to rescue phototropism o ResponseSignal Transduction Pathway 39 Chloroplast movement inside leaf cell to optimize light absorption 39 High light move to side of cells 39 Low light spread out 39 Opening of Stomata C02 diffuses into cells as blue light triggers photosynthesis RedFar Red Light Germination Stem Elongation Flowering Photosynthesis RedBlue light 0 Farred light indicates shade Phytochrome redfarred receptor 0 Photoreversibility switching between redfarred absorbtion makes photoreceptor change shape 39 PrPfr Signals that Promote Flowering 0 Flower formation begins when apical meristem stops making energyharvesting stems and leaves and makes modified stemleaf that makes ower 0 Photoperiodism response based on day length 39 Plant clocks CONSTANS C0 When phytochrome is activated by light it stabilizes CO CO accumulates in cells Gravitropism Gravity sensing takes place in root cap roots stop responding to gravity if the root caps are removed Statolith Hypothesis 0 Amyloplast organelle contains starch o Pulled to bottom of root cap by gravity 0 Position of amyloplast activates sensory proteins in plasma membrane 39 Initiate gravitropic response Auxin produced in shoot tips 0 Root cap cells sense the direction of gravity and respond by changing the distribution of auxin in root tip 0 Normal 39 Auxin ows down middle of root toward perimeter and away from root cap 0 Tipped 39 Sensory receptors trigger changes in position proteins that redistribute auxin o Auxin redistribution more at lower root less at top 0 High auxin decreases grth 39 Therefore uneven distribution causes differential grth 0 Apical Dominance 39 Growth restricted to main stems 39 Cut a stem and apply auxin the plant will grow laterally Auxin Phototropic Hormone polarunidirectional transport by parenchyma cells 0 higher concentration in shoots than roots 0 auxin overall function is signal where cells are in the plant body relative to root shoot axis 39 higher concentration closer to tip of shoot 0 Experiment blue light sensors are located at lips of coleoptiles not in the bending portionlst hypothesis that hormoses exist 39 Remove tip of coleoptile Stop bending toward light 39 Cover tips of coleoptiles Do not bend 39 Opaque collar below tip Normal bending 0 Experiment 2 Is the hormone water soluble yes 39 Cut tips off coleoptile 39 Put a porous block of agar between tip and decapitated coleoptile Behave normally 0 Therefore hormone is water soluble 39 Put a piece of mica nonporous on the decapitated coleoptile o Auxin first plant hormone discovered II indoleacetic acid 39 Promotes cell elongation in the shoot from the tip of the coleoptile o Auxin causes phototropism through asymmetrical distribution 39 Proteins found in stemleaf cells 39 Increase activity of H ATPases proton pumps in plasma membrane 39 Use energy in ATP to drive protons out of cell pH of cell wall decreases increased H acid grth hypothesis For a plant cell to grow 0 Cell wall must expand increase in volume 0 Water creates turgor pressure allow increase in volume 39 pH 45 expansin proteins are activated to unzip H bonds between cellulose microfibrils to loosen structure Cytokinins and Cell Division regulate grth by activating genes that keep the cell cycle going 0 absence arrested at G2 checkpoint Gibberellins o Stimulate grth signals germination o In stems promote both cell elongation and division ABA Abscisic acid 0 Inhibits grth seed germination o Closes guard cells in stomara 39 Transported from roots to leaves to warn of drought stress 39 Overrides bluelight photoreceptor signal and closes stomata to conserve water Open When vacuole of guard cell is filled With water cell is turgid 39 Activation of PHOT by blue light leads to water entry guard cell opening Protons pumped out of cells K and CL into guard cells 39 Activation of ABA receptors leads to water eXit HATPase is inhibited Chanels to allow Cl and anions ot leave open 0 K leaves cells and water ows out by osmosis Brassinosteriods 0 Promote grth mass Ethylene o Promotes senescence regulated process of agingdeath 39 Increases enzymes required for ripening 39 Increases cellular respiration o Transported from the leaf to the stem through the petiole 39 Weakens cell walls Beta amylase o Breaks starch bonds released in germination o Stimulated gibberellinsinhibitedaba Secondary Metabolites Closely related to compouds in synthetic pathways not found in all plants 0 Poision defenses to herbivores AuXin De nes rootshoot axis Produced in shoot apical meristems young leaves Cell elongation apical dominance Differentiation xylemphloem Phototrophismgravitropism Cytokinins Cell division Produced in apical meristems Promote cell division in the presence of auxin Break dormancy Delay senescence agin Gibberellins Stem growth Produced in apical meristems Cell elongation germination division ABA Abscisic Acid Slowprevent grth Induce stomata closure Stress hormone analalous to cortisol in humans Brassinosteroids Mass grth Promote elongation Related to steroid hormones in animals