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Article: Rhythms of Plant Life
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- Biology
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CopyrightCOPYRIGHT 2002 The Gale Group Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Rhythms of Plant Life
Plants exhibit regular, cyclic physiological changes of many sorts. For example, leaflets of wood sorrel,
Oxalis,
fold downward to a vertical position at night and return to their normal horizontal orientation during the day. Because this rhythm takes place over a period of approximately twenty-four hours, it is called a
circadian
rhythm.
Forces within the plant control the movements of wood sorrel and many other circadian rhythms. This is easily demonstrated by placing wood sorrel in total darkness for several days. In the absence of external light stimuli, the movements continue in an approximate circadian rhythm, but the period tends to lengthen slightly to ...