One of the commonly used plant growth hormone in tea plantations is

Indole-3-acetic acid (IAA) is a natural auxin.
In tea plantations the shoot tips are regularly removed; this removes apical dominance, so the lateral buds grow into branches and the bush becomes dense. This phenomenon, controlled by auxin, is widely applied in tea plantations and hedge-making.
Auxins are also used to initiate rooting in stem cuttings, which is how tea is commonly propagated.
Ethylene is used for fruit ripening, abscisic acid is a growth inhibitor, and zeatin is a cytokinin.
Hence the hormone commonly used in tea plantations is indole-3-acetic acid.