what are plant hormones? give the uses of the plant hormones like auxins,gibberlins,cytokinins and artificial hormones like ABA,ethylene??

Plant hormones are chemicals or molecules present in plants that cause certain changes in them and helps in adapting to the environment.

Auxins:  It promotes root growth at very low concentrations. It promote apical dominance and inhibits abcission.

Gibberellins: It promotes cell enlargement, bolting of some rosette plants, leaf growth while it inhibits root initiation. 

Cytokinins: It promotes cell division in apical meristem and cambium, it promotes fruit growth while it delays leaf senescence. 

Abscisic acid: It generally plays an overall inhibitory role, notably during physiological stress. It promotes bud dormancy, seed dormancy and abcission.

Ethylene: It breaks seed dormancy and promotes fruit ripening. 

Abscisic acid and ethylene are not artificial hormones and are synthesized naturally by plants.