Improving some biochemical characteristics of lemon balm (Melissa officinalis L.) with phytohormones-like activity of plant-derived smoke

In order to evaluate the phytohormones-like effects of plant-derived smoke on some biochemical characteristics of lemon balm, an experiment was conducted as a split plot in time based on complete randomized block design with three replications in research greenhouse of campus of agricultural and natural resources of Razi University in 2017. The main factor was different levels of leaf foliar application (including four concentrations of smoke-water (i.e., 1:5000, 1:1000, 1:500, and 1:100 (v/v)) accompanied with cytokinin, auxin, and gibberellic acid (each with a concentration of 50 μM), as well as the control) and the sub-factor included two harvest stages. The results indicated that the application of different concentrations of smoke-water and growth phytohormones significantly increased the content of chlorophyll and carotenoids, photosynthesis rate, transpiration rate and stomatal conductance, but reduced the accumulation of soluble carbohydrate content and the percentage of electrolyte leakage. However, chlorophyll fluorescence parameters, anthocyanin content, soluble protein content and activity rate of antioxidant enzymes were not significantly affected by foliar application levels. In general, these findings indicate that plant-derived smoke similar to growth phytohormones has a great potential to improve biochemical efficiency of lemon balm and can be considered as a natural agrochemical.