Ch37_Lecture-Spr11

Ch37_Lecture-Spr11 - Regulation of Plant Regulation of...

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Unformatted text preview: Regulation of Plant Growth 37 37 Regulation of Plant Growth • 37.1 How Does Plant Development Proceed? • 37.2 What Do Gibberellins Do? • 37.3 What Does Auxin Do? • 37.4 What are the Effects of Cytokinins, Ethylene, and Brassinosteroids? • 37.5 How Do Photoreceptors Participate in Plant Growth Regulation? 37.1 How Does Plant Development Proceed? Features that maximize plants’ ability to obtain resources for growth and reproduction: • Meristems allow growth throughout the plant’s life • Post-embryonic organ formation — new organs can develop throughout life • Differential growth — they can grow organs most needed, e.g., more leaves http://www.ncsec.org/team8/fp.gif 37.1 How Does Plant Development Proceed? Plants must monitor their environment and redirect growth as appropriate A plant’s environment is never completely stable light changes day to night, and with seasons neighbor plants compete for light, nutrients, etc. http://www.howplantswork.net/wp- content/uploads/2009/10/winding_road.jpg 37.1 How Does Plant Development Proceed? Signals (environmental cues, photoreceptors, and hormones) affect three fundamental processes: Cell division Cell expansion Cell differentiation http://aggie-horticulture.tamu.edu/faculty/davies/students/ngo 37.1 How Does Plant Development Proceed? Plant development is regulated in complex ways. Four factors regulate growth: Presence of environmental cues Receptors, e.g. photoreceptors, to sense environmental cues Hormones mediate effects of cues The plant’s genome www.ryanphotographic.com/images/Scenes/ 37.1 How Does Plant Development Proceed? Seeds are dormant — cells do not divide, expand, or differentiate As seed begins to germinate , it takes up ( imbibes ) water Growing embryo obtains chemical building blocks by digesting food stored in seed Germination is completed when radicle (embryonic root) emerges Now called a seedling http://imagessvt.free.fr/physioV/germination 37.1 How Does Plant Development Proceed? If seedling germinates underground, it must elongate rapidly, and cope with darkness for a time Series of photoreceptors directs this stage of development Early seedling development varies in monocots and eudicots Figure 37.1 Patterns of Early Shoot Development (Part 1) Figure 37.1 Patterns of Early Shoot Development (Part 2) Figure 37.1 Patterns of Early Shoot Development (Part 3) 37.1 How Does Plant Development Proceed? Seed dormancy may last weeks, months, or years. Mechanisms that maintain dormancy include: Exclusion of water or oxygen by impermeable seed coat Mechanical restraint of embryo by tough seed coat Chemical inhibition of embryo development www.aphotoflora.com Iris seeds 37.1 How Does Plant Development Proceed?...
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Ch37_Lecture-Spr11 - Regulation of Plant Regulation of...

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