The influence of prolonged but low intensity blue light on the physiological properties of root tubers and the accumulation of flavonoids in Tetrastigma hemsleyanum Diels et Gilg

Abstract

Tetrastigma hemsleyanum Diel et Gilg is a perennial herbaceous plant native to subtropical China with multiple medicinal applications. Supplementing with low-density blue light (BL) for 45 days (3 h/day) can not only significantly increase the yields of root tubers but also significantly increase the flavonoid content and its antioxidant activity. The chlorophyll content in the leaves of T. hemsleyanum significantly decreased, but the photosynthetic efficiency significantly increased after reaching the light saturation point. The production rate of superoxide anion radical in the leaves reached the highest peak after 1.5 h in BL and decreased at 3 h. The H2O2 content in the leaves decreased significantly, while the H2O2 content in the root tubers increased significantly at 3 h in BL. The objective of this research was to determine how the scavenging system, including antioxidant enzymes, antioxidants, and flavonoids respond to the oxidative stress induced by BL in root tubers. After exposure to BL, significant differences in the activity of APX and SOD were observed in the leaves and tubers within 3 h. By analyzing the upregulated flavonoids metabolites and key genes in metabolic pathways through the combined analysis of the flavonoid metabolic group and transcriptome in the root tubers, the upregulated accumulation of flavanols was found to be the main reason for the improvement in the antioxidant properties of flavonoids.