Tropisms and Nastic Movements - Research Article from Macmillan Science Library: Plant Sciences

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Tropisms

Phototropism.

Phototropism is one of the most significant tropisms for plant survival because it positions shoots where more light for photosyn-thesis is available. It is especially important during seedling emergence and when plants are shaded unequally.

Sensing. One of the first important studies of plant tropisms was of phototropism by Charles Darwin and his son Francis over a century ago. They tried to determine where light is sensed in the coleoptile, which is a leaflike sheath that covers and protects emerging grass seedlings. As in current phototropism experiments, they exposed the seedling to light from just one side. Coleoptiles whose tips were cut off or were kept dark by a hood did not grow toward the light. However, if the tips were covered by transparent material or if the base of the coleoptile was kept dark, then the coleoptiles grew towards the light. They concluded...

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This section contains 3,249 words
(approx. 11 pages at 300 words per page)
Buy the Tropisms and Nastic Movements Encyclopedia Article
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Macmillan Science Library: Plant Sciences
Tropisms and Nastic Movements from Macmillan Science Library: Plant Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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