Plant Hormones and Responses
November 16, 2007
TA: Xuecong Liu
Plant hormones, though small in quantity, have a powerful effect on a plant’s performance. Activities such as plant growth, tropisms, and changes in plant parts are all determined by hormonal control (Lum, et al., 2008).
One important plant hormone is auxin. Auxin was the first hormone to be discovered and is involved in important processes such as apical dominance and elongation. Another important substance, an important player in seed germination, is phytochrome. Phytochrome was discovered in the 1950’s by scientists Hendricks and Borthwick, who found that red light is effective in promoting germination; however, it can be reversible by far-red light. This indicated the presence of a photoreversible pigment, now referred to as phytochrome (Sage, 1992).
The present study was carried out to determine the conditions in which hormones are likely to affect the growth of various plants. For our first experiment, we hypothesized that the growth of germinating corn seeds would demonstrate positive geotropism, causing the roots to grow in the direction of gravity. In our second experiment, we hypothesized that the third pot would have the least lateral growth due to auxin inhibition. Conversely, the second pot would have the most lateral growth because the auxin would not be inhibited in any way. For our final experiment, we predicted that both the plate exposed to four minutes of red light treatment, as well as the plate that was treated with red light, followed by far-red light, and then again by red light would produce more germinated seeds than those exposed to only far-red light or the exposed to far-red light last, which should produce very few germinated seeds.
For our first experiment, we placed a lining of moist paper towels on a cafeteria tray. We placed corn seeds in different orientations on the paper towels,...