Positive Roles of Ethylene :

Negative Role of Ethylene :

Positive Role of Abscisic acid:

Negative Role of Abscisic acid:

Solution:

(a) Positive Roles of Ethylene: Ripening of fruits

– It stimulates the creation of root meristems and the growth of lateral roots when present in low concentrations.

(b) Negative Role of Ethylene:

– Ethylene is responsible for nullifying geotropism.

(c) Positive Role of Abscisic acid:

– When a plant is stressed, the concentration of abscisic acid in its leaves rises, causing stomata to close, reducing water loss by transpiration.

(d) Negative Role of Abscisic acid:

– It inhibits the growth of a plant and in turn, induces dormancy of buds.