Effect of the red light on the photosynthesis and phenolic accumulation in leaves of Hedyotis corymbosa (L.) Lam

Abstract

Hedyotis corymbosa (L.) Lam a native herbaceous species containing many phenolic compounds is used in traditional medicine and medicinal technology. Phenolic acid, as well as many other secondary metabolites are photosynthetic-derived products. In this research, red LEDs (660 nm) and white fluorescent light were used to investigate the effects of different light sources on the photosynthesis and leaf phenolic compound accumulation of in vitro and ex vitro plants. Red LED (50 umol/m2/sec) promoted the stem elongation without changing plant biomass of in vitro plants. Increasing red LED intensities (from 50 to 100 or 150 umol/m2/sec) decrease maximum photochemical quantum yield of PS II (Fv/Fm) and coefficient of photochemical fluorescence quenching (qP), but stabilized electron transfer (ETR) and coefficient of non-photochemical fluorescence quenching (qN) of in vitro leaves. Under 100 umol/m2/sec of red LED, ex vitro leaf area, carotenoid contents, isolated chloroplast. Hill reaction and total sugar content were significantly reduced in comparison to those parameters from control plants under white light. Ex vitro plants' total carbohydrate contents were not statistically different the total leaf phenolic content of ex vitro plants under red LED light exposure was much higher than that the of control.