Let's go back and revise the answer. Maybe your original title is not the English abbreviation of "synthetic plant growth regulator types", but an extra word, which makes us very confused.

Synthetic plant growth regulator. Synthetic PGR for short. However, "synthesis" can be abbreviated before.

Auxin (auxin)

gibberellin

Cytokinin (CTK)

ethylene

abscisic acid

indoleacetic acid

indolebutyric acid

Naphthylacetic acid (NAA)

Naphthyloxyacetic acid (NOA)

Dichlorophenoxyacetic acid

2,4,5-trichlorophenoxyacetic acid

2- methyl -4- chlorophenoxyacetic acid (MCPA)

Sai Wen (Sai Wen)

gibberellin

Cytokinin (CTK)

6- benzylaminopurine

Chlorobenzoic acid

Ethrel

Ethylene silicon (CGA- 1528 1)

AVG (average)

Bijiu (B9)

Chlormequat chloride

Deformed actin

Leisure element (MH)

Triiodobenzoic acid (TIBA)

Adjust phosphine (F0samine)

Paclobutrazol (paclobutrazol 1, PP333)

Uniconazole

TRIA (Tria)

Rutin

Promalin (Promalin)