Literature Review
Done by: Yeo Tzun Kai
Research Question:
How do roots grow when the direction of
gravity changes?
Hypothesis
The roots will grow towards the direction of gravity.
Hypothesis
The roots will grow towards the direction of gravity.
Introduction
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.
Bibliography
Bibliography
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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