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Responses to light are critical for plant survival . Consider a sprouting plant left in...

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ninaesl | Student, Undergraduate | eNoter

Posted May 23, 2013 at 4:34 AM via web

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Responses to light are critical for plant survival . Consider a sprouting plant left in a closet with only a horizontal sliver of sunlight soming in form the crack at the bottom of the door.

1-Explain how the plant would respond to light.

2-How it could survive as a result of its response. Refer to the action of a specific hormone and use appropriate scientific terminology in your response .

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ncchemist | eNotes Employee

Posted May 23, 2013 at 12:28 PM (Answer #1)

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The plant would alter the direction of its growth toward the available light.  The change in growth of a plant in response to an external stimulus is called tropism.  In particular, the response of the direction of a plant's growth toward light is called phototropism.  This is because, as you stated, plants need sunlight to produce food via photosynthesis to survive.

The hormone responsible for phototropism is called auxin.  It causes cells to elongate and is usually present in the cells on the shadowy side of a plant.  So the auxin in the cells not facing the sunlight will cause those cells to elongate and ultimately cause the stem to bend in the direction toward the light.  That is how phototropism works.

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