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Why does the root of a plant go away from the sun? The shoot goes towards the sun, why does the root go away from it?

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  • $\begingroup$ What do you think would happen to the direction the roots would grow, if the light source was below the plant? $\endgroup$ – Gabriel Fair Sep 15 '17 at 13:42
  • $\begingroup$ @GabrielFair I don't know sir thats why I am asking the question. If I were to guess, it goes away because it wants water and sunlight evaporates it. $\endgroup$ – Ram Keswani Sep 17 '17 at 11:13
  • $\begingroup$ can someone please answer $\endgroup$ – Ram Keswani Nov 18 '17 at 12:03
  • $\begingroup$ All you have to do is read the wikipedia page for phototropism. en.wikipedia.org/wiki/Phototropism $\endgroup$ – Gabriel Fair Nov 18 '17 at 15:43
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The roots respond to gravity, not to light. They display what is called a geotropism (aka gravitropism). It has nothing to do with the light.. The roots grow TOWARD the force of gravity so the roots exhibit positive geotropism. The stem grows AWAY from the force of gravity so it exhibits negative geotropism. Think about a tree planted on a hill.

Phototropism is a plant's response to light. It has nothing to do with the direction of room growth. The stem may lean toward the sun (because of it's positive phototropism) but will still grow upward because of its negative geotropism.

**If the light was below the plant, the roots would still grow downward.

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    $\begingroup$ This is a good answer, though we prefer answers here at Biology.SE to include some citations to support statements and encourage further reading. $\endgroup$ – Bryan Krause Jan 24 '18 at 22:32

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