Abstract
BackgroundThe optimized illumination of plants using light-emitting diodes (LEDs) is beneficial to their photosynthetic performance, and in recent years, LEDs have been widely used in horticultural facilities. However, there are significant differences in the responses of different crops to different wavelengths of light. Thus, the influence of artificial light on photosynthesis requires further investigation to provide theoretical guidelines for the light environments used in industrial crop production. In this study, we tested the effects of different LEDs (white, W; blue, B; green, G; yellow, Y; and red, R) with the same photon flux density (300 μmol/m2·s) on the growth, development, photosynthesis, chlorophyll fluorescence characteristics, leaf structure, and chloroplast ultrastructure of Welsh onion (Allium fistulosum L.) plants.ResultsPlants in the W and B treatments had significantly higher height, leaf area, and fresh weight than those in the other treatments. The photosynthetic pigment content and net photosynthetic rate (Pn) in the W treatment were significantly higher than those in the monochromatic light treatments, the transpiration rate (E) and stomatal conductance (Gs) were the highest in the B treatment, and the intercellular CO2 concentration (Ci) was the highest in the Y treatment. The non-photochemical quenching coefficient (NPQ) was the highest in the Y treatment, but the other chlorophyll fluorescence characteristics differed among treatments in the following order: W > B > R > G > Y. This includes the maximum photochemical efficiency of photosystem II (PSII) under dark adaptation (Fv/Fm), maximum photochemical efficiency of PSII under light adaptation (Fv′/Fm′), photochemical quenching coefficient (qP), actual photochemical efficiency (ΦPSII), and apparent electron transport rate (ETR). Finally, the leaf structure and chloroplast ultrastructure showed the most complete development in the B treatment.ConclusionsWhite and blue light significantly improved the photosynthetic efficiency of Welsh onions, whereas yellow light reduced the photosynthetic efficiency.
Highlights
The optimized illumination of plants using light-emitting diodes (LEDs) is beneficial to their photosynthetic performance, and in recent years, LEDs have been widely used in horticultural facilities
The intercellular CO2 concentrations (Ci) in the Y and G treatments were significantly higher than those in the other treatments, and Ci was the lowest in the W treatment (Fig. 2d). These results show that B light could improve the photosynthetic gas exchange of Welsh onion plants
The growth and development of plants is strongly influenced by the spectrum of light in their environment
Summary
The optimized illumination of plants using light-emitting diodes (LEDs) is beneficial to their photosynthetic performance, and in recent years, LEDs have been widely used in horticultural facilities. We tested the effects of different LEDs (white, W; blue, B; green, G; yellow, Y; and red, R) with the same photon flux density (300 μmol/m2·s) on the growth, development, photosynthesis, chlorophyll fluorescence characteristics, leaf structure, and chloroplast ultrastructure of Welsh onion (Allium fistulosum L.) plants. Studies have shown that the ratio of red (R) light to far-R light regulates the flowering time of Arabidopsis, providing evidence for the existence of wavelength-specific pathways in plant flowering times [13]. Chloroplast development and chlorophyll (Chl) metabolism are key components of photosynthesis in green plants, and previous studies have shown the existence of Chl synthesisrelated enzymes that regulate chloroplast development [16, 17]. In Camptotheca acuminata seedlings, R light promoted the development of chloroplasts and improved photosynthetic efficiency [20]
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