a. Increase the yield of sugar cane.

b. Promote lateral shoot growth.

c. Cause sprouting of potato tuber.

d. Inhibit seed germination.

Solution:

a. Increase the yield of sugar cane: Gibberellins

b. Promote lateral shoot growth: Cytokinins

c. Cause sprouting of potato tuber: Ethylene

d. Inhibit seed germination: Abscisic acid