Chapter39PlantSensorySystemsSignalsandResponses[1] - BLY...

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BLY 122 A. Hunter Chapter 39 Plant Sensory Systems, Signals, and Responses I. Information Processing: Plants have sophisticated systems for collecting information about their environment and for responding in ways that maximize their chances of surviving, thriving, and producing offspring. The process can be analyzed in three steps (Fig 39.1) A. Receptor cell receives an external signal and transduces it to an intracellular signal B. Receptor cell sends a signal to cells in another part of the body that can respond to the information C.) Responder cells receive this long-distance signal, transduce it to an intracellular signal and change activity. Signal Transduction (information change from an external signal to an intracellular signal 2 Types (phosphorylation cascade) and second messengers (Fig 39.2) Cells that receive information from signal transduction are not the cells that respond to the information. Signal transduction in a receptor cell often results in the release of a hormone that carries information to responder cells. Because plants perceive a wide variety of stimuli, they have a wide array of hormones. Target cells routinely receive information from several different hormones at the same time, so it is common for different types of hormones to interact with each other and modulate the cell's response. Plant hormones have several important properties in common: (1) they can elicit a response only if a cell has an appropriate receptor, and (2) they are active at extremely small concentrations. How Do Cells Respond to Cell–Cell Signals? o If a receptor on or in a cell binds to a hormone and changes shape in response, the signal at the cell's periphery is rapidly transduced to increased activity inside the cell, via s signal transduction pathway. o The phosphorylated proteins or second messengers that result from the signal transduction cascade result in changes in cell activity. o Activation of a signal transduction cascade results in the production of many phosphorylated proteins or release of many secondary messengers to amplify the original signal many times. o When cells respond to a hormone, the change in their activity helps the individual cope with the environmental change sensed by the receptor cell. Most of our general principles of plant communication emerged from studies of how plants respond to light. Light Sensing A. Plants sense different wavelengths of light and respond with particular behaviors. B. What Do Plants See? 1. What is the effect of unidirectional light on the growth of grass seedling coleoptiles?— Charles and Francis Darwin a. Experiment: Expose dark-grown coleoptiles to candlelight from one direction. b.
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This note was uploaded on 11/11/2009 for the course BLY 459 taught by Professor Obrien,j during the Spring '08 term at S. Alabama.

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Chapter39PlantSensorySystemsSignalsandResponses[1] - BLY...

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