Effect of alternating red and blue LED irradiation sequence on growth of Lettuce

Abstract

Lettuce is one of popular plants that usually used in indoor farming. Development of technology make people used LED as additional or supplementary light sources to enhance proper plant growth. However, apart from high cost in maintenance, facility design and operation, LED also increase the cost of electricity. Nowadays, people usually used combination of red and blue LED for long hours such as 16 hours or 18 hours of plant photoperiod. Hence, alternating of red and blue LED irradiation sequence on growth of lettuce is investigate to observe the effect of alternating light on the growth of lettuce and also as one of alternative in reducing th by original copyright e consumption of energy. In this study, there were three light treatments conducted with constant light intensity and under 16 hours of photoperiod. Two different R/B alternating light intervals that were respectively 4 hours and 8 hours were tested. One simultaneous light treatment (RB) was set as control. Results showed the different light treatments gives changes on plant morphology in which lettuce under R/B (4hr) was highest compared to others. The leaf width bigger for plant under simultaneous RB (16hr) followed by R/B (4hr) then R/B (8hr). There is no significant different in the number of leaf for plant under RB (16hr) and R/B (8hr). For the fresh mass and dry mass of plant is monopolize by lettuce under RB (16hr) while there is no significant different for lettuce under treatment R/B (4hr) and R/B (8hr). Meanwhile, the chlorophyll a and b are detected to be lowest in lettuce under R/B (4hr). Based on the results, it is conclude that the alternating light can affect the growth and quality of lettuce. Apart from that, light intensity also plays important role and should be consider in which it can affect the growth of plant.