Effect of Chitosan on Physiological and Morphological Traits of Lemon Verbena (Lippia citriodora L.) under in Vitro and Field Conditions

Chitosan is one of the bio-elicitors that cause physiological and morphological changes in plants. To this end, two separate experiments were carried out to investigate the effect of chitosan on morphological and physiological traits of lemon verbena under in vitro and field conditions. 12.5, 25, 50 and 100 ppm concentrations of chitosan were added to MS culture medium and their effects on lemon verbena growth indices were evaluated. The results showed that chitosan had a significant effect on all traits, except for the normal plantlet percentage, lateral shoots and chlorotic leaf numbers evaluated. Increasing chitosan concentrations up to 50 and 100 ppm under in vitro condition increased longest shoot length, chlorophyll content and plantlet length in lemon verbena explants but it reduced node numbers of the longest shoot when all concentrations of chitosan were used. Increasing the effect of chitosan on rooting percentage and root numbers were positive and reached the highest levels at concentrations of 50 and 100 ppm. It was also found that the shoot fresh weight, the leaf number and longest root have a positive effect on chitosan and had a better effect on concentrations less than 100 ppm. However, the use of chitosan showed irregular changes in the amount of citral. The effect of chitosan with 12.5, 25, 50 and 100 ppm concentrations were evaluated on growth indices of lemon verbena under field condition. The positive effect of chitosan concentration of 50 ppm was observed for inflorescence number, inflorescence length and leaf fresh weight. Because of positive effects of chitosan concentrations of 50 and 100 ppm, on most growth characteristics of lemon verbena in field and tissue culture conditions their applications could be recommended in plantations of this tree.