Growth, Photosynthetic Characteristics, Antioxidant Capacity and Biomass Yield and Quality of Wheat (Triticum aestivum L.) Exposed to LED Light Sources with Different Spectra Combinations

As a consequence of the increasing importance of crop in Bioregenerative Life Support System (BLSS), there is an interest in enhancing both the productivity and quality of wheat. Lighting systems for growing wheat need to be lightweight, reliable and durable. Light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue lights was an effective light source for several crops. Yet the appearance of plant in this kind of lighting was purplish grey, and other problems were also accompanied. The addition of other spectra LEDs made better growth and also offer a better visual experience to bring psychological benefit to the crews. The objective of this study was to investigate the influences of different spectra combinations on the wheat growth, photosynthetic characteristics, antioxidant capacity and biomass yield and quality during their life cycle. Four types of different spectra combinations with the same intensity were employed: a single red light (R), a red-blue light (R+B, R:B=4:1), a red-white light (R+W, R:W=4:1) and a white light (W). The results showed that the wheat cultivated in the R+W light was characterized by highest harvest index and lowest lignin in inedible biomass, which was more beneficial to recycle substances in the processes of the environment regeneration. The data were comparable to those under W condition in terms of straw height, relative water content (RWC), membrane stability index (MSI), photosynthetic rate, chlorophyll concentration, antioxidant capacity, thousand kernel weight (TKW) and soluble sugar concentration. Wheat was sensitive to light quality which significantly affected those indices of growth and physiology, especially at earing and flowering stages.