Bachelor’s Degree Programme (BSCG) – Plant Physiology and Metabolism Assig. Answer | BBYCT–137(Q-9)
9. a) Distinguish between short day and long day plants giving two examples of each. What is the role of phytochrome in flowering?
b) What are allosteric enzymes? Discuss with the help of an example
a) Short Day –
(i) The short day plants are those plants that bloom flower in day length shorter than the critical point.
(ii) The short day plants need continuous dark periods.
(iii) The short day plants do not bloom if the dark period is interrupted by a flash of light.
Example: Green grams, marijuana, cotton.
Long Day –
(i) The long day plants are those that bloom when they are exposed to days longer than the critical point.
(ii) The long day plants need light periods and it is critical for these plants.
(iii) The long day plants bloom more effectively if the dark period is interrupted by a flash of light.
Example: Wheat, henbane, carnation.
The roles of phytochrome are:
- It plays an important role in each and every stages of plant development.
- Pfr is a physiologically active form which inhibits flowering in short day plants and also promotes flowering in the long day plants.
b) It is a kind of enzyme which can change their structural ensemble when they bind to an effector i.e allosteric modulator, by which they can change their binding affinity at a different ligand binding site. They play a major role in various biological processes. There is a specific site to which the effector binds known as allosteric site.This site mainly allows the effector to bind to the protein, which results in conformational changes involving protein dynamics process.
Example of Allosteric Enzymes: Glucokinase
It plays a major role in homeostasis of glucose as it converts glucose to glucose-6-phosphate and increases glycogen synthesis inside the liver.
It also maintains concentration of glucose into the blood.
Their activity is regulated by glucokinase regulatory proteins.