Lecture9

Lecture9 - Calvin cycle essential for sugar production ALSO...

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1 Calvin cycle essential for sugar production ALSO interconnected with many other metabolic pathways in other compartments Plant growth and development •Overview of hormones •major chemical classes •possible signaling mechanisms •Examples of hormonal controls through life cycle •embryogenesis •germination Environmental signals: Light Temperature Gravity Water availability Salinity Pathogens Internal signals: Developmental stage Tissue/organ (position within body) Nutrient status Phytohormones Genetically programmed options Phytohormones = chemicals made by plant to regulate their own growth and development; active at very low concentrations
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2 Five classes of “classical” hormones •Small molecules: weak acids or bases, 1 gas •Can cross membrane in uncharged form •Active in nM - μM range Leaf senescence: Cytokinin (-) Stomatal opening: ABA (-), auxin (+) Embryo and seed development: All hormones at different stages Seed germination: GA (+), ABA (-) Cell/stem elongation: ABA and ethylene (-) GA and cytokinins synthesized: move to shoots Auxin and GA synthesized in young leaves and bud: move down stem Lateral bud growth: Auxin (-), cytokinin (+) All “classical” hormones have many effects in all stages of life cycle in many tissue/cell types Both positive and negative interactions among hormones Fruit growth: auxin, GA and cytokinin (+) Fruit ripening: ethylene (+) “New” hormones include lipid, oligosaccharide, steroid, and peptide (and many more) 1) biosynthesis 2) arrival at site of action
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Lecture9 - Calvin cycle essential for sugar production ALSO...

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