Exogenous application of melatonin mitigates the adverse effects of drought stress on morpho-physiological traits and secondary metabolites in Moldavian balm (Dracocephalum moldavica)

Abstract

Melatonin has emerged as an important signaling molecule that regulates plant responses to environmental stresses. In this research, melatonin was used to alleviate the adverse effects of oxidative stress induced by water deficit in Moldavian balm (Dracocephalum moldavica) plants and morpho-physiological traits were investigated. This experiment was conducted as a factorial arrangement based on completely randomized design with four replications. Treatments included foliar melatonin application at four levels 0 (distilled water), 50, 100 and 150 lM and drought stress 100 (control), 80, 60 and 40% of field capacity (FC). Higher levels of drought stress at 60% and 40% FC, caused the reduction of plant height, shoot fresh and dry weight, root length, root fresh and dry weight, photosynthetic pigments and protein content. Increased amount of soluble sugar content, malondialdehyde content and lipoxygenase activity, non-enzyme antioxidants (including flavonoid, polyphenol compounds and anthocyanin), phenylalanine ammonia-lyase and polyphenol oxidase enzymes activities were also observed at 60% and 40% FC. Melatonin at 100 lM improved morphological parameters, photosynthetic pigments and protein content under moderate and severe drought stress. The obtained results suggested that foliar application of 100 lM melatonin also alleviated oxidative burst and malondialdehyde production in Moldavian balm plant under moderate and severe drought stress probably through regulation of secondary metabolism and the enzymes activity of phenylalanine ammonia-lyase and polyphenol oxidase.

The Effect of Foliar Application of Melatonin on Changes in Secondary Metabolite Contents in Two Citrus Species Under Drought Stress Conditions

“…These results indicated that melatonin delayed aging of kiwifruit leaves by activating the antioxidant capacity and enhancing flavonoid biosynthesis. In another studies, Bahcesular et al (2020) on basil ( O. basilicum L.), and Naghizadeh et al (2019) on moldavian balm ( D. moldavica L.) observed that foliar application of 100 μM melatonin increased secondary metabolites synthesis in plant under moderate and severe drought stress probably through regulation of secondary metabolism and the enzymes activity of PAL and polyphenol oxidase. The exogenous application of melatonin can improve plant antioxidant ability by enhancing antioxidant enzyme activities and alleviating leaf senescence by improving flavonoid production ( Yin et al, 2013 ; Ben Abdallah et al, 2016 ; Liang et al, 2018 ).…”

Mechanistic insights on melatonin‐mediated drought stress mitigation in plants

“…Under drought stress, the demand for water increases, which leads to the recycling of scarce resources to reproductive sink tissues (Naghizadeh et al, 2019;. Melatonin application in Hordeum vulgare postpones induced senescence and delays the loss of chlorophyll (Li et al, 2016).…”

“…The drought response and avoidance mechanism includes the adjustment of source/sink allocation, increase in root growth, stunted growth, and shedding/senescence of older leaves (Prasad et al, 2008). Under drought stress, the demand for water increases, which leads to the recycling of scarce resources to reproductive sink tissues (Naghizadeh et al, 2019; Sadak et al, 2020). Melatonin application in Hordeum vulgare postpones induced senescence and delays the loss of chlorophyll (Li et al, 2016).…”

Foliar application of melatonin alleviates the effects of drought stress in rice (Oryza sativa L.) seedlings

“…Exogenous application of melatonin contributes to the reduction of ROS accumulation and membrane damage, as evidenced by the decrease in H2O2, electrolyte leakage, and MDA content. Additionally, melatonin has been shown to reduce electrolyte leakage and MDA content in Cucumis sativus L. and Moldavian balm under moderate and severe drought stress (Zhang et al, 2013;Naghizadeh et al, 2019). Melatonin also acts as a powerful scavenger of ROS in plants (Arnao and Hernández-Ruiz, 2015).…”