Effects of different LEDs on photosynthesis in greenhouse cucumber

This study explored the photosynthetic responses of cucumber to different light qualities from LEDs in a greenhouse. Cucumber (Cucumis sativus L. 'Shenchuni) was planted in a greenhouse with 12 h (6:00-18:00) (100 mu mol m(-2) s(-1)) top-lighting at the seedling stage and 8 h (6:00-11:00 and 16:30-19:30) interlighting (15 mu mol m(-2) s(-1)) at flowering and fruit stage by different light qualities (red:blue = 8:1 (8R1B), red:blue = 6:3 (6R3B) and red:green:blue = 6:2:1 (6R2G1B)). During the seedling stage, the net photosynthetic rate of leaves under the 6R3B treatment was significantly higher than those under 8R1B and 6R2G1B treatments, and had higher stomatal conductance, transpiration rate and chlorophyll a concentration, higher chloroplast number and more evenly and tightly organised lamella structure. During flowering and fruit stages, there was no influence on chlorophyll contents of cucumber leaves by different LEDs interlighting. In the 6R3B interlighting treatment, the net photosynthetic rate, stomatal conductance and transpiration rate were the highest. In the 8R1B treatment, there were obvious large starch grains in the chloroplasts, less regular and full chloroplast structure and no significant difference in chloroplast numbers. It was concluded that the 6R3B treatment, which had a higher proportion of blue light, could enhance the leaf photosynthetic capacity and benefit leaf chloroplast development.