Plant-derived smoke water and karrikinolide (KAR(1)) enhance physiological activities, essential oil yield and bioactive constituents of Mentha arvensis L.

INTRODUCTION: The current study was carried out with the hypothesis that foliar application of plant-derived smoke water (PDSW) and karrikinolide (KAR(1)) might enhanced the plant growth, physiology, and essential oil production of the Mentha arvensis L. Karrikinolide (KAR(1)) is one of the most important bioactive constituents of PDSW. METHODS: Mint (Mentha arvensis L.) was grown in natural conditions in the net-house. Different concentrations of PDSW (1:125, 1:250, 1:500 and 1:1000 v/v) and KAR(1) (10(-9) M, 10(-8) M, 10(-7) M and 10(-6) M) were used as foliar-spray treatments, using double-distilled water as control. The PDSW was prepared by burning the dried wheat-straw that acted as a growth-promoting substance. RESULTS: Foliar-spray treatment 1:500 v/v of PDSW and 10(-8) M of KAR(1) proved optimal for enhancing all morphological, physiological, and essential-oil yield related parameters. In comparison with the control, 1:500 v/v of PDSW and 10(-8) M of KAR(1) increased significantly (p ≤ 0.05) the height of mint plant (19.23% and 16.47%), fresh weight (19.30% and 17.44%), dry weight (35.36% and 24.75%), leaf area (18.22% and 17.46%), and leaf yield per plant (28.41% and 23.74%). In addition, these treatments also significantly increased the photosynthetic parameters, including chlorophyll fluorescence (12.10% and 11.41%), total chlorophyll content (25.70% and 20.77%), and total carotenoid content (29.77% and 27.18%). Likewise, 1:500 v/v of PDSW and 10(-8) M of KAR(1) significantly increased the essential-oil content (37.09% and 32.25%), essential oil productivity per plant (72.22% and 66.66%), menthol content (29.94% and 25.42%), menthyl acetate content (36.90% and 31.73%), and menthone content (44.38% and 37.75%). Furthermore, the TIC chromatogram of the GCMS analysis revealed the presence of 34 compounds, 12 of which showed major peak areas. DISCUSSION: Treatment 1: 500 v/v of PDSW proved better than the treatment 10(-8) M of KAR(1) with regard to most of the parameters studied. The outcome of the study can be used as a recommendation tool for agricultural and horticultural crops, since it costs much lesser than that of KAR(1). In fact, the foliar application of PDSW proved economical and played bioactive role at very low concentrations.