Fast Response - Biological Responses

Some of the fast responses are discussed below:

1. It was found that when mung bean root tips were kept in a specific solution (containing ATP, IAA, ascorbic acid, MnCl₂, KCl) the root tips adhered to a glass beaker when irradiated with red light. This effect was reversed by far-red light within 30 seconds. It is suggested that the quick response is probably due, to change in electric charges on the root tips in response to red light, so the root, tips adhere on to the negatively charged glass surface. Such a response can be classified as a fast response.
2. Similarly, it was shown that if alga, Mougeotia was irradiated, its single chloroplast turned in response to red light but far-red light alone had no effect. The red light effect was reversed by far-red light. This movement was also noticed within minutes of irradiation. In fact, in these experiments, the light was irradiated on the cytoplasm or membranes barrier and not onto the chloroplast directly.
3. In many leguminous plants it was found that leaves closed if they were transferred from light to darkness. It has been shown that this response is under phytochrome control.