NAA (alpha Naphthalene acetic acid) and 2,4 Dichlorophenoxy acetic acid are synthetic auxins. Normally, auxins inhibit flowering. In litchi and pineapple, it promotes flowering. Related Theory Antiauxins are a group of chemicals that can prevent auxin-action in plants. Transcinnamic acid, ascorbic acid, 7-phenyl butyric acid are some of these antiauxins. Probably, an antiauxin competes with an auxin for the same site of reaction and thus inhibits auxin-action.