Use of LED As Supplementary Lighting for Growing Gailan In Poly-House

A study was conducted to understand the effects of LED supplementary lighting on the growth of gailan (Brassica alboglabra) in a poly-house in Singapore. The study comprised four light treatments plus control (no supplementary lighting). The treatments involved the use of white, red and red-blue (in ratios of 8:2 and 7:3) LEDs as supplementary lighting to extend the daily photoperiod. At seven days after transplanting, treated plants were subjected to supplementary lighting of 4 hours (7 to 11 pm) beyond normal daylight hours. Vegetative parameters including total and marketable fresh-weight yield, number of leaves per plant, plant weight and length, stem length, leaf length and width and chlorophyll SPAD reading were recorded. Highest yields were obtained for gailan grown with red-blue LED as supplementary lighting. Red-blue LED also led to longer stem length as well as higher chlorophyll content. Red LED resulted in longer leaf length and higher number of leaves while white light brought about longer plant length. Leaves were also narrower under supplementary lighting compared to control. Findings showed that the use of supplementary lighting improved fresh weight yields and altered morphological characteristics of gailan. The economics of using such supplementary lighting for growing vegetables in Singapore would be discussed.