The soil characteristics and morpho-physiological traits of two violet (Viola sp.) species as influenced by gibberellic acid and nitrogen

Abstract

ABSTRACT Violet, with its pleasant scent and attractive flower color, is also important for its medicinal and edible uses, in addition to ornamental uses. Proper nutrition of the plant (violet) with essential nutrients and growth hormones improves the quantitative and qualitative characteristics and can increase the economic value and popularity of these flowers. In this regard, the current research aims to investigate the combined effect of nitrogen (N) and gibberellic acid (GA) on the morphophysiological traits of two native Iranian violet species (Viola tricolor and Viola odorata), as a factorial experiment with three factors including two species of violets, three levels of GA (0, 150 and 300 mg/L) and three levels of N (0, 100 and 200 mg/L) in a completely randomized design with 18 treatments, 3 replications and a total of 216 plants. Some characteristics of planting medium, morphophysiological traits and activity of antioxidant enzymes were evaluated. The results of ANOVA showed that the three-way effect of experimental treatments on all evaluated traits is significant. According to the results of comparing the averages the N application reduced the soil electrical conductivity (EC) versus its non-application in both violet species and at all GA levels. The highest soil N in both species was obtained from the application of 0 mg/L GA × 100 or 200 mg/L N. In two species of violets, the highest number of leaves, flowers, and stolons was obtained from the treatment of 300 mg/L GA × 200 mg/L N. The highest chlorophyll a and total chlorophyll among the treatments were related to V. odorata × 150 mg/L GA × 200 mg/L N. The application of GA and N in both species increased peroxidase activity versus the control. The highest level of this enzyme activity was related to 300 mg/L GA × 200 mg/L N. V. odorata had higher peroxidase activity than V. tricolor. The lowest and highest levels of catalase activity were recorded by control × V. tricolor (0.13 nM/g FW/min) and V. odorata × 300 mg/L GA × 200 mg/L N (0.676 nM/g FW/min), respectively. According to the results, with the application of 300 or 150 mg/L GA × 200 mg/L N, the ornamental and edible properties of these two types of violets are improved, and their economic value and marketability are increased, and there will be a change in the sales market of these flowers.