Tuesday, 9 July 2013

ISS Literature Review (Tzun Kai)

Literature Review
Done by: Yeo Tzun Kai

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

The roots will grow towards the direction of gravity.


Geotropism describes how plants respond to gravity. Roots are termed positively geotropic as they grow toward the direction of the pull of gravity. Shoots are negatively geotropic because they grow away from which also can be said as opposite the gravitational pull. If you plant a seed on its side, the shoot and root will emerge horizontally, but will quickly change their direction of growth. Within hours of germination, the shoot will bend to grow upward and the root will bend to grow downward.

Auxin was initially used to describe what were thought to be a group of chemicals responsible for promoting growth in response to stimuli. Therefore, under the influences of gravity, the Auxin migrates to the lower side of the stem. Here, the hormone stimulates growth, causing the lower side to grow more quickly than the upper, bending the stem upwards while the opposite happens to the roots. This is because in the stem, the Auxin collects in the lower side of a horizontal root. However, root cells behave differently than stem cells. Root cells elongate in response to the lower levels of Auxin in the upper surface, causing the roots to bend downward.


National Gardening Association (published in 1999) Response to light Retrieved 9 July 2013, from http://assoc.garden.org/courseweb/course1/week2/page14.htm

National Gardening Association (published in 1999) Response to gravity Retrieved 9 July 2013, from 

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