The Effect of Light Quality on Some Quantitative and Qualitative Characteristics of Fruits of Grape (Vitis vinifera L. ‘Yaghooti’), under salinity conditions in greenhouse

The purpose of this study was to investigate the effect of light quality on some fruit quantitative and qualitative traits of grape in response to the salinity of the nutrient solution in a hydroponic system in a greenhouse, The study was carried out as a factorial experiment with two factors based on a completely randomize design and three replications over two successive years. The first factor was light quality at 5 levels including red 100%, blue 100%, red and blue with a ratio of 70 and 30%, red and blue with a ratio of 50 and 50% and the control (greenhouse natural light) and the second factor was electrical conductivity caused by adding sodium chloride to the nutrient solution at 4 levels including 1.67 (control), 3.63, 6.05 and 10.23 Ms/cm. The results of this study showed that in combination of red and blue light (70-30) treatment at 10.23 Ms/cm salinity compared to other light qualities, the weight, length, width and cluster density are of fruit were 53, 71.89, 70 and 36% respectively, more than the natural light of the greenhouse. The combination of red and blue lights increased the amount of dry matter (18.31%), dissolved solids (18.31%), titratable acid (12.51%), antioxidant capacity (20%) and vitamin C (39.49%) compared to the natural light of the greenhouse. It also caused the lowest accumulation of tannin in the fruit (29.55%) in the treatment of 10.23 Ms/cm of salinity. Blue light (100%) led to an increase in the sugar to acid ratio and anthocyanin ratio by 18.31 and 37.41%, respectively, more than natural greenhouse light in grape fruit.Therefore, the combination of red and blue lights, especially the ratio of 70-30%, showed a greater effect in maintaining and improving the quantitative and qualitative characteristics of the fruit in severe salinity treatment.