Advances in Applied Agricultural Sciences 03 (2015), 04: 16-25
Light intensity affects on medicinal compound ajoene accumulation in hydroponically grown garlic plants
Most Tahera Naznin 1 ö, Yoshiaki Kitaya 1, Toshio Shibuya 1, Hiroaki Hirai 1 and Mark G. Lefsrud
1 Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Gakuen-cho 1-1, Sakai, Osaka 599-8531, Japan. 2 Bioresource Engineering Department, Macdonald Stewart Building, MS1-096, McGill University, 21111 Lakeshore, Ste-Anne-de-Bellevue, H9X 3V9, Quebec, Canada. ö Presently,Bioresource Engineering Department, Macdonald Stewart Building, MS1-096, McGill University, 21111 Lakeshore, Ste-Anne-de-Bellevue, H9X 3V9, Quebec, Canada.
Light is important for precise management of plant physiological responses and important secondary metabolite production. The objectives of this study were to determine the effects of different light intensities on tissue biomass and secondary metabolite ajoene accumulation in garlic. In this experiment, hydroponically cultured garlic plants were grown under light treatments of 75, 200, 300, and 460 mmolm-2s-1. Maximum fresh and dry mass accumulation per plant were observed under 460 mmolm-2s-1 light level. The transpiration rate, stomatal conductance, and relative chlorophyll content at 460 mmol·m-2·s–1 were 1.6, 2.1, and 1.3 times greater, respectively, than those at 75 mmol·m-2·s–1light level. The accumulation of ajoene concentration was significantly increased with increasing light intensity from 75 to 300 mmolm-2s-1. Maximum accumulation of ajoene concentration (975.3 mg/g), on a fresh mass basis, occurred under 300 mmolm-2s-1 light level but highest ajoene content (33.3 mg/plant) was observed at 460 mmolm-2s-1. Lowest accumulation of ajoene concentration (530.7 mg/g) and content (2.9 mg/plant) were observed at 75 mmolm-2s-1 light level, on a fresh mass basis.Interestingly, medicinal compound ajoene concentration increased linearly with garlic dry mass. In conclusion, the biomass accumulation were higher for plants grown at 460 mmolm-2s-1 light level but ajoene concentration accumulation were higher for plants grown at 300 mmolm-2s-1. There is a strong positive correlation with ajoene concentration with dry mass. Identifying effects of light intensity on ajoene accumulation in garlic is important information for growers producing this crop for dry capsule supplements and fresh markets vegetables.