Studying some morphological responses of stevia (Stevia rebaudiana Bertoni) to some elicitors under water deficiency

This research evaluated the effect of foliar spraying of different elicitors on modulating the effect of water stress on the stevia. The experimental design was the split-plot based on a randomized complete block design with three repetitions. Experimental treatments included different irrigation regimes (90% FC, 65% FC, and 40% FC) and foliar application of different elicitors (control, chitosan, salicylic acid, and melatonin). In this study, the content of chlorophyll A and b was reduced by intensifying the water deficit stress. Also, the highest content of the two pigments was allocated to the treatment of melatonin application. In the present study, melatonin foliar application under 90% FC irrigation conditions had the highest plant height, leaf area index, biomass, and carotenoid content, Moreover, the highest content of proline, phenol, DPPH, rebaudioside A, and steviosid was assigned to melatonin foliar application treatment under 40% FC irrigation conditions. Results revealed, although water stress reduced plant height, leaf area index, and plant biomass, the application of melatonin and salicylic acid under different irrigation conditions moderated the effect of water stress on these traits. Application of melatonin and salicylic acid under water deficit stress conditions also increased the content of proline, phenol, DPPH, rebaudioside, and steviosid.