Recurrent drought stress effects on essential oil profile of Lamiaceae plants: An approach regarding stress memory

Drought stress is of the major abiotic stress factors shifting the primary and secondary metabolism of the plants. The mechanisms corresponding to the stress-plant interaction and subsequently impacts on plants have been well-documented. However, there are insufficient documents regarding with drought experience influence on the plant metabolism. Along with the study, the drought experience on the essential oil compounds of rosemary, sage, lavender and basil leaves were for the first time- investigated. Briefly, experimental plants were firstly divided into two groups: irrigated and non-irrigated groups for seven days and then all plants were fully-irrigated as recovery stage. After recovery stage, both plant groups were divided into two more groups as irrigated and non-irrigated for more seven days. For the analysis, leaf samples were collected at Day-0, Day-7 (first cycle), Day-14 (second cycle) and Day-21 (third cycle) for each group. Since the accumulation of the secondary metabolites has been considered as an adaptive strategy of the plants in response to the stress that matters, the changes in essential oil compounds in order to investigate the possible influence of drought experience were profiled. Along with the study, specifically, the behaviour of common components including alpha-pinene, D-limonene, eucalyptol, and camphor in rosemary, sage, lavandula, and basil were assessed. Of those components, alpha-pinene decreased with the maturity and drought stress in rosemary but increased in lavender. In sage, it sharply decreased with the stress but recurrent drought increased. In basil, first stress and recurrent stress increased the percentage of the component. D-limonene increased with first and recurrent drought stress in rosemary and basil. On the other hand, the percentage decreased with the first stress but increased with the recurrent drought stress in sage and lavender. Eucalyptol increased by the maturity and drought stress in all plants. Camphor percentage increased with the first stress in all plants but the recurrent drought effects were different for all plants. The present study might be fundamental for the relevant researches and forthcoming studies are required to be addressed on molecular, physiological and biochemical responses associated with essential oil production.