Hi this question is for Biology 425 Plant Physiology On the North American conti

Question

Hi this question is for Biology 425 Plant Physiology

On the North American continent, poplar trees (Populus species) grow over a wide range of habitats, from far northern Canada all the way into the southern United States and Mexico. These plants are deciduous, dropping their leaves in the fall and over-wintering with dormant buds. They are genetically adapted to their environments such that they “break bud” at an appropriate time and expand their leaves when it has become warm enough to grow and carry out photosynthesis. This was shown experimentally by transplanting a northern species, that would normally break bud in May, to a southern habitat, and observing that the plant still did not break bud until May, even though the weather was quite warm in February. The conclusion was that the timing of bud break depends on plant perception of daylength, at least in poplars. Within the dormant buds are apical meristems that will begin to grow by cell division and cell expansion when the appropriate cue arrives. Starting with the knowledge that daylength is the environmental signal required by the buds, answer the following questions:

a) What photoreceptor do you hypothesize detects daylength in this case?
b) Where do you think the photoreceptors are located in the dormant poplar trees?
c) Briefly describe an experiment you could do to test your idea above.
d) Experimental measurements indicate that gibberellin levels in the buds rise concurrently with bud break. You might conclude that synthesis of this hormone is directed by the photoreceptor’s detection of appropriate daylength. Describe the results of an experiment that would demonstrate that gibberellin is able to cause “bud break.”

Explanation / Answer

a) Phytochromes (PHY b) are the photoreceptors that detects daylength in case of Poplar trees.

b) Photoreceptors are present in the Grana and Stroma of the thylakoid membrane in the Chloroplast of the leaves in the dormant popular trees.

c) A benchpoint of bud dormancy is the cessation of cell division at the apical meristem. The signalling mechanisms regulating the cell cycle during growth cessation and dormancy induction, identified two cyclin-dependent kinases (CDKs) which regulates the orderly phase transitions that occur during the cell cycle.

d) Gibberellin has a significant effect on promoting dormancy.  In popler trees, as ABA levels decrease, growth commences as gibberellin levels increase. If the hormone Gibberellin is applied exogenously, it promotes flowering in LDP (Long Day Plants), induce parthenocarpy (seedless fruits), increase the size of flower and fruit, and break dormancy of seed and buds.

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.