Steam distillation of essential oil crops produces residual distillation wastewater that is released into the environment. This study evaluated the effects of three plant hormones [methyl jasmonate (MJ); gibberellic acid (GA3); and salicylic acid (SA)] at three concentrations and the residual distillation water from 15 plant species applied as foliar spray on biomass yields, essential oil content, and essential oil yield of Mentha ×piperita ‘Black Mitcham’ and Mentha spicata ‘Native’. Overall, the application of SA at 1000 mg·L−1 increased biomass yields of both species. More treatments influenced essential oil content in ‘Black Mitcham’ peppermint than in ‘Native’ spearmint. Application of MJ at 100 and 1000 mg·L−1, GA3 at 10 mg·L−1, SA at 10 or 100 mg·L−1, and distillation water of Achillea millefolium, Ammi majus, Artemisia absinthium, Cymbopogon flexuosus, Cymbopogon martinii, Chrysanthemum balsamita, and Hypericum perforatum increased the essential oil content of peppermint, whereas the oil content of spearmint was increased only by application of Monarda fistulosa distillation water. Application of MJ at 100 mg·L−1, SA at 100 mg·L−1, and A. absinthium, C. flexuosus, and C. balsamita distillation waters increased essential oil yields of peppermint, whereas the application of SA at 1000 mg·L−1 and distillation water of A. absinthium, Lavandula vera, and M. fistulosa increased oil yields of spearmint. This study demonstrated that the residual distillation water of some aromatic plant species may be used as a tool for increasing essential oil content or essential oil yields of peppermint and spearmint crops.
The Influence of Different Drying Methods on Essential Oil Content and Composition of Peppermint (Mentha piperita L.) in Çukurova Conditions
