Light quality-dependent regulation of photoprotection and antioxidant properties in rice seedlings grown under different light-emitting diodes

We examined light quality-dependent regulation of photoprotection and antioxidant properties in rice seedlings. Seedlings grown under red or green light-emitting diodes (LEDs) showed declines in quantum yield of electron transport through PSII, maximum relative electron transport rates, and photochemical quenching compared to the white and blue LED, but no difference in maximum photochemical efficiency of PSII was found. Blue LED treatment resulted in greater increases in not only nonphotochemical quenching, but also zeaxanthin formation, expressions of β-carotene hydroxylase and violaxanthin de-epoxidase, and anthocyanin compared to other LED treatments. By contrast, green and red LEDs increased activities of superoxide dismutase and ascorbate peroxidase as well as expression levels of catalase (CAT)a and CATb to white and blue LEDs. Green and red LEDs also greatly upregulated expressions of phytochrome (PHY) A, PHYB, PHYC, and cryptochrome 2 compared to white and blue LEDs, whereas blue LED upregulated CRY1. Our results demonstrate that specific wavelengths of different LEDs differentially influence photosynthetic performance, photoprotection, and antioxidant properties, possibly through regulating expressions of phytochrome and cryptochrome genes in a light-quality-dependent manner.