rav65819_ch41_801-826

Rav65819_ch41_801-82 - 41 chapter ALL ORGANISMS SENSE AND INTERACT with their environments This is particularly true of plants Plant survival and

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;;;;;;;; 41 chapter ALL ORGANISMS SENSE AND INTERACT with their environments. This is particularly true of plants. Plant survival and growth are critically influenced by abiotic factors, including water, wind, and light. The effect of the local environment on plant growth also accounts for much of the variation in adult form within a species. In this chapter, we explore how a plant senses such factors and transduces these signals to elicit an optimal physiological, growth, or developmental response. Although
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responses can be observed on a macroscopic scale, the mechanism of response occurs at the level of the cell. Signals are perceived when they interact with a receptor molecule, causing a shape change and altering the receptor’s ability to interact with signaling molecules. Hormones play an important role in the internal signaling that brings about environmental responses and are keyed in many ways to the environment. Sensory Systems in Plants introduction 41.4 Responses to Water and Temperature Dormancy is a response to water, temperature, and light Plants can survive temperature extremes concept outline 41.1 Responses to Light Phytochromes initiate signal transduction Many growth responses are linked to phytochrome action P fr facilitates expression of light-response genes Light affects directional growth Circadian clocks are independent of light but are entrained by light 41.2 Responses to Gravity
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Plants align with the gravitational feld: An overview Stems bend away From a center oF gravity Roots bend toward a center oF gravity 41.3 Responses to Mechanical Stimuli Touch can trigger irreversible growth responses Reversible responses to touch and other stimuli involve turgor pressure 41.5 Hormones and Sensory Systems The hormones that guide growth are keyed to the environment Auxin allows elongation and organizes the body plan Cytokinins stimulate cell division and diFFerentiation Gibberllins enhance plant growth and nutrient utilization Brassinosteroids are structurally similar to animal hormones Oligosaccharins act as deFense-signaling molecules Ethylene induces Fruit ripening and aids plant deFenses Abscisic acid suppresses growth and induces dormancy 801 rav65819_ch41_801-826.indd 801 rav65819_ch41_801-826.indd 801 11/30/06 4:05:42 PM 11/30/06 4:05:42 PM 41.1 Responses to Light In chapter 8 we covered the details of photosynthesis, the process by which plants convert light energy into chemical bond energy. We described pigments, molecules that are capable of absorbing light energy; you learned that chlorophylls are the primary pigment molecules of photosynthesis. Plants contain other pigments as well, and one of the functions of these other pigments is to detect light and to mediate plants’ response to light by passing on information. Several environmental factors, including light, can initiate seed germination, flowering, and other
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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Rav65819_ch41_801-82 - 41 chapter ALL ORGANISMS SENSE AND INTERACT with their environments This is particularly true of plants Plant survival and

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