Question

Name a plant hormone which inhibits growth

Answer 1

Abscisic acid (ABA) is a  plant hormone which functions mainly as a growth inhibitor. 
Abscisic acid promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy]. 
It also promotes closing of stomata. 
Abscisic acid promotes falling and wilting of leaves 

Answer 2

Auxins, especially 1-Naphthaleneacetic acid (NAA) and Indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants. The most common auxin found in plants is indole-3-acetic acid or IAA. The correlation of auxins and cytokinins in the plants is a constant (A/C = const.).

Hope this helps you..