Control of growth and flowering of chrysanthemum (Dendranthema x grandiflorum Kitam.) using day length extension and Red Light Night Break

Abstract

In tropical areas, since the day length (DL) is shorter than the critical DL for chrysanthemum (Dendranthema x grandiflorum Kitam.), chrysanthemum flowers before reaching the required stem length (SL) for cut flower. Two experiments were conducted with the aim of determining critical DL for vegetative growth of chrysanthemum genotype; to attain a required SL and promote vegetative growth of chrysanthemum using night break (NB) with red light for spray type of chrysanthemum. In the first experiment, DL was extended by one, two, and three hours using white fluorescent light (WL) after sunset. In the second experiment, red light (RL) was applied at the middle of the night for 15, 30, or 45 minutes to break the night. The experiments were laid out in completely randomized design with four replications. The results indicated DL extension with WL and RL night breaks had significant effect on vegetative characters and biomass yield. Similarly, flower bud initiation, coloring and blooming were significantly affected. NB using RL had a significant effect on flower diameter. The three hours DL extension (12+3 hours) totally inhibited flowering of chrysanthemum genotype, which can be considered a critical DL for Hawa1. NB with RL for 15, 30, or 45 minutes effectively inhibited flowering of chrysanthemum. In conclusion, breaking the night with RL at the middle of the night for 15 minutes with small amount of intensity (9.42 |µmolm-2s-1) is enough to inhibit flowering and promote stem elongation of chrysanthemum Hawa1.