Effects of Light Quality on Growth and Flavonoids of Adzuki Bean Sprouts and Its Preliminary Mechanism

In order to provide a basis for the regulation of the light environment in factory production for the growth of Adzuki bean sprouts,the optimal light quality and photoperiod were explored. Adzuki bean sprouts were cultured under darkness(D),white light(W),blue light(B),ultraviolet A(UV-A)and ultraviolet B(UV-B)to study the effects of different light quality on adzuki bean sprout growth and flavonoid contents,and to preliminarily investigate the flavonoid synthesis mechanism. The results showed that,compared with W treatment, the UV-B treatment significantly decreased plant height, edible fresh weight and moisture content of adzuki bean sprouts. Compared with D and W conditions,the other light treatments significantly(p<0.05)increased the total flavonoid content of adzuki bean sprouts,and the UV-B treatment had the greatest effect. Additionally,rutin and kaempferol contents significanthy(p<0.05) increased in response to the UV-B treatment. Moreover,the exposure to different UV-B duration decreased the moisture content and 4 h UV-B duration was resulted in ideal adzuki bean sprout growth and nutrient contents. The flavonoid content continued to increase under UV-B light for up to 120 h. Chalcone synthase(CHS)and flavonol synthase(FLS)activities were consistently higher under UV-B than under W for up to 60 h. Furthermore,the UV-B treatment upregulated the expression of the related enzyme-encoding genes. Therefore,exposure to UV-B light could significantly increase(p<0.05)the abundance of flavonoids and their monomers in adzuki bean sprouts by enhancing CHS and FLS activities and the expression of the corresponding genes.