This research investigated the effect of light quality on changes in leaf pigments, photosynthesis rate, and gas exchange in grapevine under salinity stress in greenhouse. The study was conducted as a factorial experiment based on a completely randomized design with three replications over two consecutive years. The first factor was light quality generated by LED lamps at 5 levels, including: 100% red, 100% blue, 70% red + 30% blue, and 50% red + 50% blue and the control (greenhouse natural sunlight). The second factor was electrical conductivity (EC) induced by adding NaCl to the nutrient solutions at 4 levels, including 1.67 (the control), 3.63, 6.05, and 10.23 dS.m-1. The results indicated that under the EC of 10.23 dS.m-1, both combinations of red and blue lights (especially 70-30% ratio) led to a greater increase and preservation total Chlorophyll contents, stomatal conductance and carboxylation efficiency in leaves compared to the monochromatic lights, while they reduced substomatal CO2 concentration. 100% blue light had the highest effect on reducing the leaf surface temperature followed by greenhouse natural sunlight, whereas 100% red light had a substantial impact on reducing the transpiration rate. 100% red light, along with both the combination of red and blue, showed the highest actual water use efficiency under the EC of 10.23 dS.m-1. According to the results, both the combinations of red and blue improved the plant's tolerance and continuous photosynthetic activity under salinity stress conditions by increasing the positive effects or reducing the negative effects of salinity.
Keshavarzi et al. (Wed,) studied this question.