Effect of Gibberellic Acid and Monophenols on Flowering of lmpatiens balsamina in Relation to the Number of Inductive and Non‐inductive Photoperiodic Cycles

Abstract

AbstractA single treatment of plants with GA3 (gibberellic acid) is not adequate to cause induction under LD (long day: 24‐h photo‐period) condition, but its effect is added to the sub‐threshold induction caused by one SD (short day: 8‐h photoperiod) cycle. Floral bud initiation is hastened, and the number of floral buds and flowers per flowering plant increases in plants receiving a single treatment with the combination GA3+ SA (salicylic acid) accompanying a single SD cycle. However, the increase on 10 replicate basis is more marked in plants receiving three treatments with the combination GA3+β‐N (β‐naphthol) and five treatments with the combination GA3+ SA accompanying six and 10 SD cycles, respectively. The number of floral buds and flowers decreases with an increase hi the number of SD cycles, but it is higher in plants treated with GA3, SA or GA3+β‐N than in the water‐treated controls. — Under long days, treatment of plants with the combinations GA3+ SA or GA3+β‐N accelerates the initiation as well as increases the number of floral buds. While a minimum of five treatments with GA3 or of 25 with SA or β‐N alone is needed for floral bud initiation under a 24‐h photoperiod, three treatments are adequate to induce floral buds with the combination GA3+ SA or GA3+β‐N under continuous illumination. Ten or more treatments with these combinations under a 24‐h photoperiod produce more flowers than the same treatments under an 8‐h photoperiod.