Effect of ascorbic acid on morpho-physiological characteristics and production of Stevia rebaudiana (Bert.)

Stevia rebaudiana (Bert.) is an herbaceous perennial plant of the Asteraceae family, native to Paraguay. To study the effect of foliar application of ascorbic acid on growth indices of stevia, an experiment based on randomized complete block design with three replications was conducted at the University of Zanjan, Iran. Four levels of ascorbic acid (0, 0.5, 1, 2 mM) were applied three times after the establishment of transplants in the field at 10 days intervals. Factors including plant height, number of branches, number of nodes, number of leaves plant^‑1, leaf fresh and dry weight plant^‑1, total fresh and dry weight plant^‑1, total flavonoid, phenol, and total chlorophyll were studied. Based upon statistical analysis, the results showed that ascorbic acid significantly influenced the above-mentioned characteristics. The highest average plant height (46.77 cm compared to 37.33 cm in control) was recorded in 2 mM ascorbic acid. The highest number of nodes (23.33 compared to 18.00 in control), number of leaves plant^‑1 (957.67 compared to 608.33 in control), leaf fresh weight plant^‑1 (127.13 g compared to 63.18 g in control), and leaf dry weight plant^‑1 (37.13 g compared to 17.48 g in control), total flavonoid (11.09 mg g^‑1 DW compared to 7.42 mg g^‑1 DW in control), phenol (26.36 mg g^‑1 DW compared to 16.05 mg g^‑1 DW in control), total chlorophyll (4.60 mg g^‑1 FW compared to 3.72 mg g^‑1 FW in control) were recorded in 1 mM ascorbic acid. Collectively, the results showed that the application of ascorbic acid significantly improved phytochemical characteristics, physiological indices, and production of Stevia rebaudiana.