Exogenous applications of gibberellic acid modulate the growth, flowering and longevity of calla lily.

Calla lily (Zantedeschia aethiopica (L.) Spreng.) is an important ornamental crop used in garden landscapes, floral arrangements, and medicinal applications. Gibberellic acid (GA3) is actively involved in cell elongation, growth, physiology, and flowering. In addition, it is an environmentally-friendly compound which can be applied to plants to increase the ornamental production. Therefore, the present study was designed with three GA3 spray times viz., single, double and triple spray and five exogenous applications of gibberellic acid concentrations viz., 0, 25, 50, 100, and 200 mg L-1 with factorial randomized block design. Results revealed that the interaction effect of combinations of two time applications of GA3 at 100 mg L-1 induced higher growth parameters over control. Significantly higher physiological parameters viz., photosynthetic rate (14.3 µmol m-2s-1), number of stomata (26.5 mm-2), stomatal conductance (0.28 mmol m-2s-1), and transpiration rate (3.6 mmol m-2s-1) were reported when plants were treated twice with 100 mg L-1 GA3. Similarly, among flowering traits, days to flower were significantly low in plants treated two-time spray at GA3 100 mg L-1 (169.8 days). The number of flowers in the double spray at GA3 100 mg L-1 treatment increased by 11.3 and 23.7% over triple spray and control, respectively. Vase life was also significantly higher in plants treated with double spray at GA3 100 mg L-1 (6.3 days). The regression equation and correlation matrix indicated a strong relationship between growth, flowering and GA3 concentrations up to 100 mg L-1. The PCA analysis revealed that the calla lily crop is positively affected by spray timing and GA3 treatments. In the context of vegetative, reproductive, and longevity parameters of the crop, a dual spray of 100 mg L-1 GA3 can be recommended to small scale farmers and commercial growers as an alternative technique for promoting growth, yield and improving the ornamental value for commercial level production.