lecture 2-22 plants IV - Chapter 39 (pp.788-802) Plant...

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Unformatted text preview: Chapter 39 (pp.788-802) Plant hormones: Development and responses Learning objectives: Explain what etiolation is. What is de-etiolation? Describe the signal pathways associated with de-etiolation. Describe the two main mechanisms by which a signaling pathway can activate an enzyme. Know the major functions of these plant hormones: auxins cytokinins gibberellins brassinosteroids abscisic acid ethylene. Be able to discuss the role of hormones in examples such as cell elongation, cell differentiation, leaf abscission, seed dormancy, seed germination, fruit ripening, plant stress Explain why 2,4-D is an effective weed killer Review: Signal transduction pathway steps: 1. Reception Internal and external signals are detected by receptors (proteins) that change in response to specific stimuli (ligands) 2. Transduction Signals are transferred (and amplified) to proteins that cause specific responses 3. Response One or more cellular activities are regulated, usually by increased activity of certain enzymes At the time of germi-nation, the seedling plant has a single root-shoot axis. Primary growth consists of the elongation and branching of the root(s) and shoot(s). Secondary growth is a progressive thickening of roots and shoots that can continue for many years following their initial (primary) growth, and is restricted to woody plants such as trees or bushes. Plants have signal transduction pathways A potato left growing in darkness Will produce shoots that do not appear healthy, and will lack elongated roots These are morphological adaptations for growing in darkness Collectively referred to as etiolation Figure 39.2a (a) Before exposure to light. A dark-grown potato has tall, spindly stems and nonexpanded leavesmorphological adaptations that enable the shoots to penetrate the soil. The roots are short, but there is little need for water absorption because little water is lost by the shoots....
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This note was uploaded on 03/19/2008 for the course BIO 311D taught by Professor Reichler during the Spring '08 term at University of Texas at Austin.

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lecture 2-22 plants IV - Chapter 39 (pp.788-802) Plant...

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