Different combinations of red and blue LED light affect the growth, physiology metabolism and photosynthesis of in vitro-cultured Dendrobium nobile ‘Zixia’

The aims of this study were to evaluate how different light qualities alter the physiological and biochemical characteristics, of Dendrobium nobile. To determine the best light quality for in vitro culture of D. nobiles plantlets, the relationships between growth, antioxidant capacity, nutrient and chlorophyll contents, and chlorophyll fluorescence were evaluated. Growth under five Light-Emitting Diode (LED) light treatments, red light (R), blue light (B), 8R:2B, 7R:3B, and 5R:5B, were compared to white fluorescent light. The 8R:2B and 7R:3B mixtures of red and blue LED light were beneficial to root number, root length, root activity, fresh and dry weight, antioxidant ability, and chlorophyll content and fluorescence. The carotenoid content and ΦPSII significantly correlated with root length, while NPQ significantly correlated with root activity, length of root, fresh and dry weight and SSC. qP was significantly correlated with fresh and dry weight and the activities of FPC, POD and APX. Comprehensive scores, derived from Principal Component Analysis (PCA), of the plants grown under the 8R:2B and 7R:3B light treatments were similar to each other, while significantly higher than plants grown under the other light treatments. In conclusion, D. nobile seedlings grown under 8R:2B and 7R:3B exhibited suitable plant architecture for the controlled environment.