Review PLS 360 exam 2 - Ethylene and abscission Endosperm...

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Ethylene and abscission Endosperm, Cotyledon = seed storage Anthers, stamen= male part Programmed cell death example is leaves falling off the tree in autumn Potato= asexual reproduction via a tuber Post-embryonic development Mammals contain nearly all of their “parts” at birth: limbs, organs, bones Plants grow organs through this Hormones mediate post-embryonic growth: Nutrient-rich soil causes less root growth and more lateral shoot growth by inducing cytokinin Cutting off the top of a plant induces more lateral shoot by cutting off the auxin supply Flooding causes taller plants by inducing active gibberellin production Embryogenesis Embryonic development is very ordered Root apical meristem: cells for root growth Radicle: the embryonic root Hypocotyl: embryonic stem Cotyledons: embryonic leaves, food storage Shoot apical meristem: cells for aerial growth Auxin is a major contributor of plant form by influencing phyllotaxis, organogenesis, and apical dominance Phyllotaxis Alternate, decussate (opposite), spiral, whorled Organogenesis Auxin has polar movement, auxin maximum on a certain spot where next leaf primordia forms Axillary buds/meristems come from SAM Undifferentiated cells left behind De-differentiation is associated with auxin In a root, promotes becoming meristems Adventitious growth Can get shoots or roots from any cell *CQ: which hormone commonly counteracts Auxin? Cytokinin Cytokinin also contributes to plant form by counteracting auxin and redistributing nutrients from roots to shoots Cytokinin responses Promote nutrient redistribution and communicate nutrient status Promotes shoot growth Cytokinin and floral architecture
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Higher levels of cytokinin increase rice yield by increasing growth and changing shoot architecture Gibberellin has a minor role in plant form by controlling stem elongation Human uses of GA Shorter plants- The Green Revolution One of the most significant scientific advances of the 20 th century was the breeding of semi-dwarf grain varieties with reduced GA responses in stems but not flowers -Advantages: Can put more energy into grain, lodging (less mold) GA responses Stress responses- rapid stem elongation during flooding However; this only works during slow flooding (needs to have respiration) Flash flooding causes plant death by extreme growth and depletion of nutrients GA has a major influence on germination and developmental transitions in response to environmental signals Delagras- repression Seed germination GA induces germination after a period of dormancy GA produced from the embryo causes synthesis of amylase in the aleurone to breakdown starch to sugar in the endosperm *CQ: Which hormone counteracts GA’s role in germination?
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