Alternating high and low intensity of blue light affects PSII photochemistry and raises the contents of carotenoids and anthocyanins in pepper leaves

The aim of the present study was to evaluate the morphological and physiological response of pepper plants (Capsicum annuum L.) as affected by different light regimes. In this context, we hypothesized that the illumination with proportionally high blue light under low light conditions induces stress-related responses and leads to stronger accumulation of protective pigments. For this purpose, pepper plants of the cultivar Yolo Wonder B were cultivated in a climate chamber under compact fluorescence lamps (CFL) or light emitting diodes (LED). Light provided by LEDs was composed by either 15 or 75 % of blue, and completed by red light. In general, high blue light led to a stronger increase in heat dissipation, whereas the maximal photochemical efficiency remained almost unaffected. Biomass formation was lower under the LED light as compared to plants grown under CFL. However, different amounts of blue light did not impact plant morphological parameters such as stem length, leaf area and plant FM. Concentration of Chl a + b was significantly higher in plants grown under CFL, whereas the Chl a/Chl b ratio and leaf mass per area were increased under the LED treatments. In general, plants grown under blue and red LEDs accumulated significantly more flavonoids compared to plants grown under CFL. Additionally, the illumination with high blue light increased the synthesis and accumulation of anthocyanins and carotenoids, whereas flavonoid contents were not affected.