Comparison of Growth, Development, and Photosynthesis of Petunia Grown Under White or Red-blue LED lights

Abstract

Red-blue (RB) LED lighting systems are widely used for plant cultivation because red and blue light are effectively absorbed by photosynthetic pigments. However, numerous studies have shown that RB LED light is either comparable to or less effective than white light in supporting plant growth. In this study, we compared the effects of RB or white LED light on growth, development, and photosynthesis of petunia (Petunia × hybrida Vilm.) plants. The plants in both treatments had similar shoot fresh weights, but the plants grown under white LED light had significantly higher shoot dry weight than those grown under RB LED light. Petunia plants grown continuously under RB light exhibited the higher single-leaf CO2 assimilation rate at 9 weeks after sowing but the lower maximum quantum efficiency and operating efficiency of PSII than those grown under white LED light. In another experiment, petunia plants were grown continuously under white LED light before measurements of single leaf CO2 assimilation rate and canopy apparent photosynthesis (CAP) under RB or white LED light. It was found that single leaf CO2 assimilation rates under RB light were higher than those under white light. However, CAP measured under RB light was either similar to or lower than that in plants measured under white LED light. White LED light had higher percentages of light transmission through the leaves than RB LED light. Results from this study suggest that white LED light could be more effective at supporting petunia plant growth than RB LED light because of its greater ability to transmit through leaves and drive photosynthesis at the canopy level.