An assessment of the physicochemical characteristics and essential oil composition of Mentha longifolia (L.) Huds. exposed to different salt stress conditions

Abstract

Salt stress adversely influences growth, development, and productivity in plants, resulting in a limitation on agriculture production worldwide. Therefore, this study aimed to investigate the effect of four different salts, i.e., NaCl, KCl, MgSO4, and CaCl2, applied at various concentrations of 0, 12.5, 25, 50, and 100 mM on the physico-chemical properties and essential oil composition of M. longifolia. After 45 days of transplantation, the plants were irrigated at different salinities at 4-day intervals for 60 days. The resulting data revealed a significant reduction in plant height, number of branches, biomass, chlorophyll content, and relative water content with rising concentrations of NaCl, KCl, and CaCl2. However, MgSO4 poses fewer toxic effects than other salts. Proline concentration, electrolyte leakage, and DPPH inhibition (%) increase with increasing salt concentrations. At lower-level salt conditions, we had a higher essential oil yield, and GC–MS analysis reported 36 compounds in which (−)-carvone and D-limonene covered the most area by 22%–50% and 45%–74%, respectively. The expression analyzed by qRT-PCR of synthetic Limonene (LS) and Carvone (ISPD) synthetic genes has synergistic and antagonistic relationships in response to salt treatments. To conclude, it can be said that lower levels of salt enhanced the production of essential oil in M. longifolia, which may provide future benefits commercially and medicinally. In addition to this, salt stress also resulted in the emergence of novel compounds in essential oils, for which future strategies are needed to identify the importance of these compounds in M. longifolia.

Melatonin application in in vitro conditions may modulate the phyto-biochemical mechanisms of Hymenocrater longiflorus Benth. under salinity stress

“…Moreover, we detected more secondary metabolites in the plants grown in the media containing melatonin and salt separately than in the control plants.Ben Ayed et al (2022) revealed that the percentage of terpenoids was signi cantly affected by increasing salinity, probably due to NaCl's induction of the speci c enzymes involved in the biosynthesis of these compounds. Moreover, a study on Mentha longifolia showed that salt stress increased carvone and limonene contents by regulating the expression of key genes responsible for the biosynthesis of these compounds(Singh et al 2023). Based on the ndings of this study, applying suitable concentrations of melatonin to plants exposed to salt stress mitigates the adverse impacts of salt stress on the levels of terpenoids, including α-pinene, copaene, β-eudesmol, terpinen-4-ol, amorpha-4,11-diene, ar-curcumene, and epicubenol.…”