Effects of Monochromatic Light Irradiation by LED on the Internodal Stem Elongation of Seedlings in Eggplant, Leaf Lettuce and Sunflower

Abstract

In this study, light emitting diodes (LEDs) used sole light source to study the effects of monochromatic light plant cultivation. (were) Seedlings of eggplant, leaf lettuce and sunflower were irradiated at 50, 100 and 150μmol m ^-2 s^-1 PPFD of blue, blue-green, green and red monochromatic lights, respectively. On 25 days from the start of monochromatic light irradiation for eggplant and leaf lettuce and on 42 days from the start of monochromatic light irradiation for sunflower, seedlings were harvested and measured. Stem elongation of eggplant and sunflower were obviously promoted under blue light, and slightly promoted under other monochromatic lights. However, stem elongation of leaf lettuce was promoted under red, green and blue-green lights, but markedly suppressed under blue light. Furthermore, changes in the ratio of petiole length to total leaf length depended on plant species and light quality. These findings indicated that growth responses to respective monochromatic lights differed among plant species.