Growth inhibiting substances

a) Ethylene (CH 2 =CH 2 ):

• Ethylene exerts a variety of effects on plants, viz., chlorosis, leaf abscission, epinasty, stimulation of adventitious roots, fruit ripening and increased permeability of cell membranes.
• Ex: Ethylene is involved in premature ripening of fingers in banana infected by Pseudomonas solanacearum, the causal agent of moko disease of banana.

b) Abscissic acid:

• It exerts dormancy in seeds, closure of stomata, inhibition of seed germination and growth and stimulated germination of fungal spores.

c) Dormin / Abscissin II:

• Dormin induces dormancy by converting developing leaf primordia of a bud into bud scales .