The Effects of Gibberellic Acid and Nitrogen on Edible Traits of Sweet Violet (Viola odorata) and Commercial Violet (Viola tricolor)

The cultivation of edible flowers, e.g. violet, which is native to Iran, is a good way to increase the availability of these new and nutritionally valuable sources to humans. This research employed a factorial experiment based on a randomized complete block design in three replications to explore the interactive effects of gibberellic acid (GA) at three rates of 0, 150, and 300 mg L-1 and nitrogen (N) at three rates of 0, 100, and 200 mg L-1  on the traits of two violet species (Viola tricolor and V. odorata). The results showed that the application of GA and N significantly improved the edible traits of both species so that the highest protein, carotenoid, Fe, and Zn contents in the petals of both species were related to the treatment of ‘GA300 × N200’. The maximum petal anthocyanin content was produced by the treatment of ‘GA0 × N100’ (58.32 mg 100 g-1 FW) in the sweet violets and by the treatment of ‘GA300 × N100’ (66.84 mg 100 g-1 FW) in the commercial violets. The commercial violets were richer in Se than the sweet violets. The highest Se contents in the commercial violets were obtained from the treatments of ‘GA300 × N200’, ‘GA300 × N100’, and ‘GA150 × N200’. In both violet species, the highest flavonoid contents at the wavelengths of 300 and 330 nm were related to the treatments of ‘GA300 × N200’ and ‘GA150 × N200’. However, these treatments were ineffective in flavonoids at 270 nm. The sweet violets had a higher antioxidant capacity than the commercial violets. The highest antioxidant capacity in the sweet violets (84.83 % DPPHsc) and commercial violets (78.17 % DPPHsc) was produced with the application of ‘GA150 × N200’. Based on the results, both species are effective sources of proteins, minerals, and antioxidant compounds. As well, ‘GA300 × N200’ and ‘GA150 × N200’ are recommended for improving the edible traits of these two species.