Plant Biology Questions- Please answer thoroughly and accurately! 5. You are the
ID: 259137 • Letter: P
Question
Plant Biology Questions- Please answer thoroughly and accurately!
5. You are the studying the light responses of a rare plant species that appears to have two photoreceptors for red light - phytochrome (PHY) and another photoreceptor X. If germinating seeds are left on top of the soil and exposed to light immediately after planting, they show early flowering. You have to determine if this effect is due to PHY or the new photoreceptor X which has been found in this exotic species. You perform 4 simple tests using different types of light treatments and obtain the following results:
Red light treatment: Early flowering
Far Red light treatment: Late flowering
Red light followed by Far Red light: Early flowering
Far Red light followed by Red light: Early flowering
Using these results, state whether the photoreceptor that promotes early flowering is likely to be PHY or the strange new receptor X. Justify your answer.
6. Phytochrome-deficient seedlings can be differentiated from wild type when they are grown in the light but not in the dark. What is the basis for this observation? What type(s) of phytochrome proteins are not expected to be detected in wild type seedlings grown in the light.
Explanation / Answer
Answer-5
Red light followed by Far Red light: Early flowering-in this observation the response should be reversed (characteristic of phytochrome) when exposed to far-red light soon after the red treatment but this is not happening in this case. So the response of early flowering is due to photoreceptor X.
Answer-6
phyA is light-labile( phyA is most abundant in dark-grown seedlings, whereas its level drops rapidly upon exposure to R or white (W) light), whereas phyB-phyE are light stable (In light-grown plants, phyB is the most abundant phytochrome, whereas phyC-phyE are less abundant)