A. Ethylene is a hormone which is gaseous in nature.
B. Auxin (synthetic auxin 2-4 D) is responsible for phototropism and geotropism in plants.
C. Ethylene causes feminising effect. External supply of very small quantity of ethylene can increase the numberof female flowers and hencefruits as in cucumber. D. Synthetic auxin (2-4 D) kills broad leaved dicot weeds, hence used as weedicides. E. Gibberellins, induces flowering in long-dayplants.