Question

P, Q, R, S are four major types of phytohormones.
P is a phytohormone which functions mainly as a growth inhibitor. It promotes the wilting and falling of leaves.
Q, R, and S are phytohormones which all promote the growth of the plant in various ways.
Q is responsible for the phenomenon of phototropism in plants.
R is involved mainly in shoot extension.
The phytohormones S helps in breaking the dormancy of seeds and buds.
What are P, Q, R, and S?

Answer 1

Hint: Plant hormones control all aspects of plant development and growth, from embryogenesis, the regulation of organ size, pathogen defense, stress tolerance and through to reproductive development. Unlike in animals (in which hormone production is restricted to specialized glands) each plant cell is capable of producing hormones.

Complete Answer:
- Phytohormones are chemical messengers that coordinate cellular activities. Some examples of phytohormones are - auxin, cytokinin, gibberellic acid, brassinosteroids, ethylene, abscisic acid, salicylic acid and jasmonic acid etc. The signal transduction, biosynthesis, transport, perception and downstream effects of each are introduced, as well as a few ways that hormonal signaling pathways intersect.
- P is abscisic acid which is responsible for wilting and falling of leaves.
- Q is auxins which are the reason for the phenomenon of phototropism in plants i.e plants curve towards the light.
- R and S are gibberellins which increase the axis length in plants or shoot extension and also help in breaking the dormancy of seeds and buds.

Note: Plant hormones are not nutrients, but chemicals that in tiny quantities and impact on the growth, development, and differentiation of cells and tissues. The biosynthesis of plant hormones within the plant tissues is eventually diffuse and not always confined. Plants lack glands to produce and store hormones, because, unlike animals—which have two circulatory systems (lymphatic and cardiovascular) powered by a heart that moves fluids around the body—plants use more passive means to move chemicals around their bodies.