Effect of salicylic acid, glycine betaine and gamma amino butyric acid as foliar application on physiological indices of bitter melon (Momordica charantia L.) under water deficit Stress

In order to investigate the effect of foliar application of salicylic acid, glycine betaine and gamma amino butyric acid on the physiological characteristics of bitter melon (Momordica charantia L.) under water deficit stress, a split plot experiment was conducted as randomized complete block design with three replications at Zanjan University in 2017. The treatments consisted of three levels of irrigation (50, 75 and 100% field capacity) as the main factor and two levels of salicylic acid (2 and 4 mM), glycine betaine (50 and 100 mM) and gamma amino butyric acid (10 and 20 mM) with control, as sub factor. The results showed that increased water deficit decreased total chlorophyll content and vitamin C content. While increasing in water deficit increased the amount of anthocyanin, carotenoids, total phenol, flavonoids and soluble solids. The highest total chlorophyll )1.62 mg/g) content was obtained in irrigation level of 100% field capacity with 50 mM glycine betain. Application of 50 mM glycine betaine in 50% of field capacity irrigation produced the highest levels of carotenoids (0.79 mg/g) and anthocyanins (5.51 µM/g). The maximum amount of phenol (20.11 mg/g) and flavonoid (4.41 mg/g) was obtained in 50% field capacity and 100% glycine betaine, respectively. Application of 4 mM salicylic acid at irrigation level of 100% of field capacity increased significantly in vitamin C (65.45 mg/g) content. The highest amount of soluble solids (7.18%) was obtained in100 mM glycine betaine in 50% field capacity water deficit. According to the results, application of different levels of glycine betaine in stress conditions is recommended to redress water deficit stress and improve the physiological properties of bitter melon.