Effect of organic priming on germination characteristics and enzyme activity of Lemon balm (Melissa Officinalis L.) under drought stress conditions

Plant germination and establishment is one of the challenges of farmers in arid and semi-arid areas, and organic priming is a suitable solution to reduce environmental pollution caused by the use of chemical inputs. For this purpose, a factorial research was carried out in the form of a completely randomized design on the seeds of Lemon balm (Melissa Officinalis L.) in three replications in the seed technology laboratory of the Islamic Azad University, Karaj branch. The treatments of this experiment include five levels of priming (chitosan, humic acid, vermicompost, distilled water and control (no prime)) and four levels of drought stress (0, 0.3, 0.6, 0.9 Mpa). The results showed that drought stress decreased the germination percentage, growth, and quality of lemongrass seedlings in non-prime conditions, and as the intensity of drought stress increased, the growth of seedlings decreased. Chitosan, humic acid, and vermicompost priming was more effective than distilled water priming (hydropriming) in increasing germination characteristics and coping with drought stress, and reduced the negative effects of drought stress. Seed priming with the mentioned treatments caused a decrease in proline concentration and ascorbate peroxidase enzyme activity. Priming with humic acid and vermicompost in non-stress conditions led to 19.52% and 19.93% germination increase in lemon balm respectively, compared to the treatment without priming and 0.9 MPa drought stress conditions.