Light quality plays an important role in all growth and development stages particularly in photosynthesis properties of plant species. The light-emitting diodes (LEDs) present maximum efficiency on biological processes among artificial lighting systems. The current study was aimed to investigate different LED light color (Blue, Red and White) and glycine concentrations (0, 40 and 80 mg L1 ) on photosynthetic efficiency of black henbane (Hyoscyamus niger L.) plant in a completely randomized design (CRD) with three to five replications. Results showed that the maxiumu quantum yield of PSII (0.839) was obtained in R LED light spectrum exposed plants upon glycine treatment at 80 mg. L1 , howevre, the lowest Fv/Fm (0.659) was detected in plants subjected to W LED spectrum. The highest Fv/Fo was obtained in plants grown under R LED lighting with glycine treatment at 80 mg. L1 ; however, C (normal light conditions) showed the lowest Fv/Fo among the light treatments. Under B LED light conditions, Δb*, ΔE*, ΔC* and Δh* were increased in comparison with normal light condition. Results showed that changing trends of these traits were consistent with those of chlorophylls and carotenoids contents under different LED-based light regimes. Moreover, compared with chlorophylls content under B LED light spectrum with glycine, the carotenoids content under W LED light source was found to be a dominant pigment in black henbane plants.
