bio 311D Exam 3 - Plant responses to the Environment: light...

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Plant responses to the Environment: light phytochrome, touch, herbivory 1) Light a. Blue purple red=most effective for photosynthesis b. Seeding germination depend on light (red=germinates) far red=does not germinate c. Phytochrome=a reversible receptor i. Red light activates phytochrome=photosynthesis occur ii. Color blinds=lacks receptors. d. Shade Avoidance i. Growing in shade under a plant grows only tall not wide./ competes with other plants 2) Touch a. Wind=shorter. b. When touched leaves fold and releases acids c. Bad touch: herbivory i. Systemin=Jacsmonic acid—volatile gas chemical/plants warn other plants/ make it difficult to digest ii. Insect saliva can let plants know which insect is attacking iii. Plants release several volatile chemicals to signal other organisms Plants grown in dark=tall. Short day plants/ long day plants Plants use day length to synchronize flowering. Critical period is actually night length Phytochrom regulates flowering time./ sets circadian clock. -Responses: Seed germination, flowering, photo morphogenesis, leaf expansion, chloroplast development, stem elongation Plants use night length to determine the season Circadian clock is unknown/ daily patters set by light. Light input oscillator output Input=resets clock Oscillator=central pacemaker that generates the oscillation/sets patterns in light/dark cycle. Output=translates oscillation into behavioral and physiological rhythms CCA1=transcription factor that regulates some photosynthetic genes. Overexpression of CCA1 in transgenic Arabidopsis plants abolished the circadian rhythms of several genes with dramatically different phases. No CCA1 protein, phytochrome induction of Lhcb RNA is reduced. Part of oscillator, but not the oscillator clock Plants were created that lack of functional CCA1 gene Plants overexpression CCA1 delayed flowering Leaf movement rhythms were abolished. Plant Reproduction Outside flower=petal=how animals recognize flower Male parts=Stamen a. Anther=pollens b. Filament Female parts= Carpel a. stigman=pollen lands b. style=long tube connecting c. ovary=contains egg 3 Nuclei a. 2 sperm nuclei -pollen tube=pollen extend cell/ can grow long -sperm fuse with egg=zygote=develops into embryo surrounded by endosperm and seed coat=seed -polar nuclei=endosperm/ haploid, triploid Seed must contain enough nutrients to nourish the embryo until it can begin photosynthesis Seed size= good indicator of how much energy is stored to support early seeding growth. Fruits=animals can get nutrients to disperse seeds. Ex. Capsacin is a deterrent to seed eating mammals. -mice(seed predator) doesn’t eat Capsacin bc of spice -Birds (seed disperser) unaffected by capsacin Cloase relatives have a higher probability of carrying the same genetic defects -decreases genetic diversity. How to Avoid inbreeding
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This note was uploaded on 06/16/2009 for the course BIO 53665 taught by Professor Iverson during the Spring '07 term at University of Texas at Austin.

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bio 311D Exam 3 - Plant responses to the Environment: light...

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