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Plant Growth and Hormones: Unveiling the Secrets of Growth and Development in Plants

Explore the fascinating world of plant growth and hormones, from the specific regions of growth like meristems to the effects of key hormones like auxin, gibberellins, abscisic acid, and ethylene. Discover how plants regenerate new cells, undergo primary and secondary growth, exhibit apical dominance, and ripen fruits through intricate hormonal processes. Learn about the evolutionary advantages of phenomena like leaf shedding in autumn and apoptosis in plants. Delve into the mechanisms behind plant growth and hormone functions to understand the complex yet beautifully orchestrated processes within the botanical realm.

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Plant Growth and Hormones: Unveiling the Secrets of Growth and Development in Plants

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  1. Plant Growth & Hormones

  2. Growth in Plants • Specific regions of growth: meristems • stem cells: perpetually embryonic tissue • regenerate new cells • apicalshoot meristem • growth in length • primary growth • apical root meristem • growth in length • primary growth • lateral meristem • growth in girth • secondary growth

  3. Apical meristems shoot root

  4. Where will the carving be in 50 years?

  5. Plant hormones • auxin • gibberellins • abscisic acid • ethylene • and more…

  6. Auxin (IAA) • Effects • controls cell division & differentiation • phototropism • growth towards light • asymmetrical distribution of auxin • cells on darker side elongate faster than cells on brighter side • apical dominance

  7. Gibberellins • Family of hormones • over 100 different gibberellins identified • Effects • stem elongation • fruit growth • seed germination plump grapes in grocery stores have been treated with gibberellin hormones while on the vine

  8. Abscisic acid (ABA) • Effects • slows growth • seed dormancy • high concentrations of abscisic acid • germination only after ABA is inactivated or leeched out • survival value: seed will germinate only under optimal conditions • light, temperature, moisture

  9. Ethylene • Hormone gas released by plant cells • Effects • fruit ripening • leaf drop • like in Autumn • apoptosis One bad apple spoils the whole bunch…

  10. Fruit ripening • Adaptation • hard, tart fruit protects developing seed from herbivores • ripe, sweet, soft fruit attracts animals to disperse seed • Mechanism • triggers ripening process • breakdown of cell wall • softening • conversion of starch to sugar • sweetening • positive feedback system • ethylene triggers ripening • ripening stimulates more ethylene production

  11. Apoptosis in plants What is the evolutionary advantage of loss of leaves in autumn? • Many events in plants involve apoptosis • response to hormones • ethylene • auxin • death of annual plant after flowering • senescence • differentiation of xylem vessels • loss of cytoplasm • shedding of autumn leaves

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