Effect of ϒ-aminobutyric acid (GABA), humic acid and salicylic acid on some ‎morphophysiological responses and antioxidant characters of Catharanthusroseus L‏.‏‎ (G.Don)‎

Periwinkle plant Chatarantus roseus L. from Apocynaceae family is one of the valuable ornamental-medicinal plants. In order to evaluate the effects of ϒ-aminobutyric acid, humic acid and salicylic acid on some characteristics of periwinkle an experiment was conducted based on complete randomized design (CRD) with three replications at Agriculture Faculty university of Zanjan. Treatments included ϒ-aminobutyric acid (0.5, 0.75 and 1 mM), humic acid (50, 100 and 150 mg.L-1) and salicylic acid (0.5, 1 and 2 mM). The results showed that highest plant height, stem diameter and leaf number was achieved 0.5mM concentration of ϒ-aminobutyric acid which had a significant difference whit the control treatment. The lowest days to flowering were 0.5 mM salicylic acid. Foliar application of 2 mM salicylic acid was significant (p<0.01) on plant height, stem diameter, phenol, peroxidase and catalase activities in compared to the control treatment. Between the different treatments, the concentration of 50 mg.L-1humic acid had the highest effect on flavonoids content. Also, plant height, stem diameter, day to flowering, peroxidase and catalase activity significantly increased in the concentration of 150 mg.L-1 humic acid compared to control treatment. Between all treatments, the highest catalase activity was observed in 2 mM salicylic acid and the highest peroxidase activity was observed in 1 ϒ-aminobutyric acid and 2 mM salicylic acid treatments. Therefore, the yield, physiological and phytochemical indices of the periwinkle improved by using of ϒ-aminobutyric acid, humic acid and salicylic acid.