Changes in photosynthesis and biosynthesis of secondary metabolites in the leaves of Schisandra chinensis under different light intensities.
Description
Schisandra chinensis, one of the traditional medicinal plants, is a mountain vine. Among the environmental factors for these plants, light conditions such as light intensity are important. The aim of this study was to evaluate the changes in photosynthetic properties and secondary metabolites of two-year-old S. chinensis saplings under different light intensities and to clarify their relationship. The results showed that under medium light intensity (240 mmol m-2 s-1) the photosynthesis improved, including 1.27 times faster net photosynthetic rate than the control. However, under lower light intensity (130 mmol m-2 s-1), photosynthesis showed to be slightly inhibited, but no significant difference from the control was observed. The contents of chlorophyll a, b and carotenoids were highest under medium light intensity (1.93, 0.12 and 0.63 mg/g, respectively). Under shade condition, the synthesis of lignans and phenolics, the major secondary metabolites of S. chinensis, also increased. The total amount of six lignans was about 1.24 times higher under medium light intensity and 1.16 times higher under lower light intensity than the control. Schisandrin and schisantherin A reached their maximum values (5.02 and 0.63 mg/g DW, respectively) under moderate light intensity, while schisandrol B and schisandrin C recorded their maximum values (2.11 and 0.23 mg/g DW) under mild light intensity. Among the 13 phenolic compounds identified in S. chinensis leaves, seven phenolic compounds increased in content under moderate light intensity. Under mild light intensity, the contents of four phenolic compounds increased while only two phenolic compounds increased in the control. The results of the study suggested that light irradiation of different intensities could affect photosynthesis and secondary metabolism of S. chinensis leaves, enhancing their medicinal value.