Tuesday, 9 July 2013

ISS Literature Review [Ikmal]

Question: How do roots grow when the direction of gravity changes?

Hypotheses: The roots would grow towards the ground.


Plants respond to earth’s gravitational attraction, and also to light. Stems grow upward towards light. Roots grow downward and away from light. These responses are called tropisms. Plants’ growth in response to gravity is known as gravitropism; the growth response to light is phototropism. Both tropisms are controlled by plant growth hormones.

Gravitropism is a plant's growth response to gravity. This occurs because of the plant hormone also called auxin that plays a part in gravitropism. When the plant is laid on its side, the auxin concentration increases along the lower sides of the roots and stems of the plant. The auxin stimulates cell elongation on the stem which makes the stem bend up toward the sky. The auxin prohibits cell elongation in the roots which causes the roots to bend down into the soil. Gravitropism allows the plant to respond to gravity no matter what position the plant is in.


http://herbarium.desu.edu/pfk/page8/page9/page9.html Retrieved on 9 July, 2013 Biology of Plants, 6th ed. Raven, Peter H., Everert, Ray F., Eichhorn, Susan E. Worth Publishing 1999. 

Botany: An Introduction to Plant Biology. Mauseth, James D. Jones and Bartlett Publishers. Sudbury, Massachusetts 1998.

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