Comparison of the efficiency of some different Zn sources on quantitative and qualitative yield of Lemon verbena

One of the most effective micronutrients in quantity and quality of medicinal herbs is zinc (Zn). The present study aimed to assess the impact of the foliar application of various Zn sources (0.2% w/v) including Zn chelated by amino acid (ZnAAC), Zn-sulfate and Zn-EDTA on qualitative and quantitative features of Lemon verbena (Lippia citriodora L.). The field experiment was performed in a randomized complete block design with three replications. Foliar application of treatments was conducted three times with one-month interval. Based on the findings, it was indicated that ZnAAC treatment has the highest effect on quantitative and qualitative characteristics of lemon verbena in comparison with other treatments. The maximum chlorophyll concentration, leaf area, leaf dry weight, essential oil content, and total antioxidant capacity (TAC) in both harvests were found in ZnAAC treatment. It was also found that Zn-sulfate was more effective compared to ZnEDTA in the studied characteristics. It was demonstrated that regardless of the source of applied Zn, all Zn application had a significant impact on all features in comparison with the control. The analysis indicated that citral (10.4-20.2), geranial (11.4-23.2), neral (7.93-18.6), truns-caryophyllene (2.34-3.22) and 1,8-cineol (1.01-1.35) were the predominant compounds in the essential oil in both harvests. The highest and lowest amounts of geranial, neral, and citral in both harvests were measured in ZnAAC (56.81%) and ZnEDTA (48.05%) treatments, respectively. Based on the findings, it seems that using ZnAAC can enhance the quantitative and qualitative characteristics of the lemon verbena.