|MadSci Network: Botany|
Gillian, I am unfortunately not aware of any easy way to inhibit the action of abscisic acid in plant geotropism. The best way to approach the action of abscisic acid in geotropism would probably be to obtain a strain of the plant which can no longer sythesize abscisic acid, e.g. because of a mutation in a gene coding for an enzyme in the pathway leading to the synthesis of abscisic acid. Several websites that might interest you are: http://www. plant-hormones.bbsrc.ac.uk/education/Kenb.htm and: http://www.abscisicacid.com /overview.htm David Hershey adds the following: Geotropism is considered an obsolete term. Gravitropism is the preferred term. One way to overcome gravity is to use a clinostat, which slowly rotates a plant about its long axis. A simple clinostat can be built using an electric alarm clock, black plastic 35 mm film can, and tape. Carefully remove the second hand from the clock and tape the lid of the film can to the clock's minute hand. The center of the lid should be lined up with the post holding the minute hand. The top of the lid should face the clock. Operate the clinostat with the clock in normal position and support the film can so the clock only has to rotate the can, not support its weight. Germinate 1 small seed (such as chia, tomato or Wisconsin fast plant) in the center of each of several 35 mm film cans by placing several moist squares of paper towel or filter paper on a 35 mm film can lid. Spray some water on the inside of the film can to prevent too much evaporation from the paper towel. Then place the film cans on the lids. After the seedling shoot has emerged and cotyledons expanded, do the experiment: 1. For the control. Turn the planted film can on its side and anchor so it doesn't roll. 2. For the treatment, place a planted film can on the clinostat. 3. Compare orientation of the shoot on the clinostat after a few hours to the control shoot.
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