Differences in plant growth and leaf sesamin content of the lignan-rich sesame variety 'Gomazou' under continuous light of different wavelengths

Sesamin is a major lignan constituent of sesame seeds and beneficial to human health. We previously reported that sesamin is contained in leaves as well as seeds of sesame and proposed that sesame leaves could be a new sesamin source. Growth and constituents of plants are affected by light wavelength. In this study, growth and leaf sesamin content of sesame variety 'Gomazou' were investigated in plants grown under continuous white fluorescent and monochromatic red or blue light emitting diode (LED) light. Under red LED light, plants developed pale-green, epinastic leaves. Compared with white fluorescent light, red LED light promoted stem elongation 1-3 weeks after sowing but retarded it 3-5 weeks after sowing. Under blue LED light, plants exhibited interveinal necrosis in the leaf blades and excessive stem elongation occurred irrespective of plant age. Leaf yields were lower in plants grown under red and blue LED lights relative to those under white fluorescent light. Blue LED light increased leaf sesamin content by 2.0 and 4.5 times compared with white fluorescent and red LED lights, respectively. From these results, we concluded that blue (LED) light may be effective at producing sesamin-rich leaves if the unfavorable morphological changes and reduction in growth can be prevented.