Rhizomes Priming with Smoke-Water and Karrikinolide Enhance the Production of Essential Oil and Bioactive Constituents of Mentha arvensis L. via Improving the Growth and Physiological Attributes of Plant

Plant-derived smoke-water (PDSW) as well as karrikinolide (a constituent of PDSW) plays a significant role in seed germination, seedling growth and other physiological attributes with regard to several medicinal and aromatic plants. To ascertain the effect of PDSW and karrikinolide, a rhizome soaking experiment was conducted on mint (Mentha arvensis L.), which is a perennial plant, carrying medicinal, aromatic, antiseptic and anaesthetic properties. Prior to planting, mint rhizomes were soaked for 24 h with aqueous solutions of various concentrations of PDSW (1:125 v/v, 1:250 v/v, 1:500 v/v and 1:1000 v/v) and KAR(1) (10(-9) M, 10(-8) M, 10(-7) M and 10(-6) M), employing double distilled water as control treatment. Rhizome soaking with 1:500 v/v concentration of PDSW and 10(-8) M concentration of KAR(1) increased the growth attributes including plant height (23.03% and 22.5%), fresh weight (23.30% and 20.98%), dry weight (44.40% and 33.55%), leaf area (26.72% and 25.67%) and leaf yield per plant (28.37% and 28.26%) as compared to the control. As a result of application of PDSW (1:500 v/v) and KAR(1) (10(-8) M), leaf physiological parameters, viz. chlorophyll fluorescence (10% and 8%), PSII activity (23% and 25%) and total content of chlorophyll (30% and 37%) and carotenoids (22% and 28%) were also significantly increased. In addition, the two treatments, viz. 1:500 v/v of PDSW and 10(-8) M of KAR(1), increased the essential oil productivity per plant by 56%. These treatments also increased the menthol content by 34% and 33% and menthyl acetate content by 47% and 46%, menthol productivity per plant by 65.71% and 64.42%, and menthyl acetate productivity per plant by 81.52% and 80.43%, respectively. Considering most of the growth, physiological and essential oil parameters studied, PDSW seemed to prove better than KAR(1), though the differences between the values were not very high. Nonetheless, PDSW may be recommend for farmers because it is far cheaper than KAR(1) (cost of 25 mg of KAR(1) = $ 4210.00).