How are gibberellins useful in agriculture to improve productivity. Give any three points in support of your answer.

3

(a)

The role of ethylene and abscisic acid is both positive and negative. Justify the statement.

3

(a)

Both animals and plants grow. Why do we say that growth and differentiation in plants is open and not so in animals? Does this statement hold true for sponges also?

3

(a)

Nicotiana tobacum,(tobacco) a short-day plant, when exposed to more than the critical period of light fails to flower. Explain.

3

(a)

If the critical photoperiod for a short-day plant is 13hrs of daylight, will it flower when there are 15 hrs of daylight?

3

(a)

Would a defoliated plant respond to photoperiodic cycle? Why?

3

(a)

Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?

3

(a)

Which areas of plant show elongation phase? Why?

3

(a)

An owner of an apple orchard wants to get better yield and wants to wait for good market conditions to sell his apples. Which PGR should he use to achieve his goals?

3

(a)

What is heterophylly?

3

(a)

What do you understand by apical dominance?

3

(a)

What are the favourable conditions for seed germination?

3

(a)

Explain some internal causes of seed dormancy.

3

(a)

What are the various man-made meant of overcoming seed dormancy?

3

(a)

Explain some natural means of overcoming seed dormancy.

3

(a)