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Plant “Behavior”

Plant “Behavior”. Plant “Behavior”. How do roots “know” to grow down? How do stems “know” to grow up? Chemicals (hormones) that control, direct, and regulate plant growth Hormone: substance produced in one part of an organism and affects another part of the same individual. Plant Hormones.

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Plant “Behavior”

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  1. Plant “Behavior”

  2. Plant “Behavior” • How do roots “know” to grow down? • How do stems “know” to grow up? • Chemicals (hormones) that control, direct, and regulate plant growth • Hormone: substance produced in one part of an organism and affects another part of the same individual

  3. Plant Hormones • Auxins – stimulate cell elongation (growth upward and downward) • Cytokinins – stimulate cell division and growth of lateral buds (sideways growth) • Cause dormant seeds to sprout • Gibberellins – produce dramatic increases in size (particularly in stems and fruit) • Ethylene – stimulates fruit to ripen

  4. Plant Responses • Tropisms – plant responses to external stimuli • Gravitropism: plant response to gravity • Involves auxins • http://www.youtube.com/watch?v=mYZXax8V_L0 • Phototropism: plant response to light • Involves auxins • http://www.youtube.com/watch?v=Ze8NV7cvW8k • Thigmotropism: plant response to touch

  5. Nastic Movements • Plant movements that occur in response to environmental stimuli but unlike tropic movements, the direction of the response is not dependent on the direction of the stimulus • Example: Venus fly trap • http://www.youtube.com/watch?v=O7eQKSf0LmY

  6. Photoperiodism • Responsible for the timing of seasonal activities, such as flowering and growth • Regulated by a pigment that absorbs red light

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