LED-Supplied Red and Blue Light Alters the Growth, Antioxidant Status, and Photochemical Potential of in Vitro-Grown Gerbera jamesonii Plantlets

Light is one of the most important environmental factors influencing plant growth and development. Light-emitting diodes (LEDs) are are a promising alternative to conventional light sources for plant tissue cultures. Combined red (R) and blue (B) LEDs are suitable for the production of many plant species. However, few studies have examined the effects of different R:B ratios on Gerbera jamesonii under controlled conditions. G. jamesonii plantlets were grown in controlled conditions under different ratios of discreet and blue light wavelengths provided by programmable LEDs. The effects of the different LED treatments on various morphological indices, photosynthetic parameters, soluble sugar and protein contents, and antioxidant enzyme activities were analyzed. Growth under monochromatic red light resulted in the tallest plantlets and longest stomata, and most promoted soluble content and intercellular CO2 concentration (C-i). Growth under monochromatic blue light promoted the highest levels of soluble protein, chlorophyll a (chlorophyll a (Chl a), and chlorophyll b (chlorophyll b (Chl b). An R:B ratio of 6:4 was the ideal LED treatment for enhancing leaf length, root length, and peroxidase activity. Growth under R:B = 7:3 promoted the number of leaves, leaf width, number of roots, superoxide dismutase, and catalase activities, chlorophyll synthesis, and the accumulation of Chl a and Chl b and led to the highest fluorescence parameters. With the exception of three physiological indicators, other indicators growth under R:B = 7:3 were better than under other tested ratios, implying that R:B = 7:3 represents the ideal LED treatment for improving G. jamesonii growth and photosynthetic activities under controlled conditions.