Responses of mixed light-emitting diode ratios on vegetative, flower regulation, and stalk elongation of cut chrysanthemum (Dendranthema grandiflora Tzvelev)

A Greenhouse experiment on the study of responses of mixed light-emitting diode ratios in cut chrysanthemum (Dendranthema grandiflora Tzvelev) was conducted at the Department of Floriculture and Landscape Architecture, Tamil Nadu Agricultural University, Coimbatore during 2019-20. The experiment was laid out in Randomized Block Design with three replications. The treatment comprises of seven varied light-emitting diode irradiance levels viz., L1 – 100% White; L2 – 100% Red; L3 -  80% Red + 20% Blue; L4 – 80% Red + 20% Far-red; L5 – 75% Blue + 25% Far-red; L6 – 60% Red + 20% Blue + 20% Far-red; L7 - High pressure sodium vapour lamp (as check) in Salvador and Pusa Centenary varieties. The results revealed that the growth in terms of height of the chrysanthemum at critical stages was maximum (48.88 cm in Salvador and 41.92 cm in Pusa Centenary) under the light irradiance of B75FR25 (L5) during the peak vegetative stage and registered maximum leaf area. Highest internodal length  up to 3rd leaf of 1.07 cm was registered in sodium vapour lamp irradiance (L7) and 1.39 cm in 100% Red irradiance (L2). The early flower bud emergence (39 days in Salvador and 50 days in Pusa Centenary) was observed in B75Fr25 spectral irradiance (L5). The highest total cut stem yield per square meter (42.65 in Salvador and 41.99 in Pusa Centenary) was registered in R80B20. The study revealed that blue LEDs combined with Far-red promoted early flowering and inhibited stem elongations. Red and Blue wavelength increased the total leaf area and registered improved flower yield.