Response of growth, photosynthetic electron transfer, and chloroplast ultrastructure to different LED light combination in green onion (Allium fistulosum L.).

ABSTRACT

With the rapid development of facility agriculture, it has become popular to study the influences of different light qualities on the growth, material metabolism, and morphology of horticultural crops. Last several years, green onions cultivation models have undergone major changes, and facility cultivation has developed rapidly. To determine the impact of light quality on the green onions, we studied the parameters connected to photosynthesis, incorporating growth, and development, photosynthetic rate (Pn ), chlorophyll fluorescence, light response curve, photosynthetic electron transfer, and chloroplast ultrastructure. We roundly analyzed the influences of different LED light combination (white W, white-blue combination 31WB, white-green combination 31WG, white-yellow combination 31WY, and white-red combination 31WR, light intensity 500 ± 10 µmol photons m-2 s-1 ) on the photosynthetic performance of green onions. The WB light led to better results than those of the WR, WG, and WY. There were significant performance improvements in leaf area, plant height, stem thickness, relative growth rate (RGR), pigment content, photosynthetic capacity, photosynthetic electron transfer efficiency, and chloroplast ultrastructure integrity. In contrast, plants treated with WG and WY were exposed to appreciably blocked light, but they effectively formed a light protection mechanism. The results of this research not only provided insight into the response mechanism of crop photosynthesis to different light qualities, but they also provided a scientific foundation for better planting green onions.