Foliar-applied melatonin modulated drought stress through modifying some important physiological and phytochemical characteristics in Taxus baccata L.

Aims: Due to its curative anti-cancer properties, the evergreen tree yew (Taxus baccata L.) was well-known before recently. Water deficit is one of the most important environmental issues that has a detrimental influence on plant biochemical and physiological processes. By regulating plant processes at the molecular level, melatonin (MT), as a bioactive elicitor, helps plant growth and withstand stress. The goal of this research was to ascertain the impact of exogenous MT on several crucial phytochemical and physiological characteristics of yew under water scarcity. Methods: Under drought stress conditions (40, 60, 80 and 100% Field capacity (FC)), MT was applied on the leaves of yew plants at concentrations of 100, 200, and 300 µM. Results: Exogenous application of MT (200 µM) caused varied biochemical responses and the highest shoot and root weight in plants. During mild drought stress, MT application increased RWC and chlorophyl content. Also, MT-treated plants in conditions of moderate drought stress (i.e., 60% FC) had higher essential oil (EO) content and yield than untreated plants. α-Pinene and β-Myrcene, as two main compounds, were highest in plants not treated with melatonin under severe drought stress (40% FC). The highest E-β-Caryophyllene and α-Humulen (two other major components) were obtained from 200 µM and control, respectively, under 100% FC. Conclusions: This research can be viewed as a useful approach to alleviate the negative impacts of water deficit stress, especially on pharmaceutical products, because the use of melatonin boosted the growth and phytochemical properties of yew in this work. [ABSTRACT FROM AUTHOR]