The potential of melatonin in the mitigation of adverse effects of salt stress in basil (Ocimum basilicum L.) plants.

backgroundDrought and salinity are among the most critical abiotic stresses affecting crops worldwide. Within this context, melatonin has emerged as a multifunctional signaling molecule that mitigates stress and promotes growth in various plant species. This study aimed to evaluate the physiological and biochemical responses of Ocimum basilicum plants cultivated under hydroponic conditions and exposed to salt stress, following pre-harvest treatment with melatonin. Basil seedlings were immersed in melatonin solutions at concentrations ranging from 0 to 100 μM for 48 hours and subsequently grown for 60 days under saline stress.

resultsMelatonin treatment, particularly at 50 μM (T50), significantly increased the fresh weight of both aerial parts and roots. Aerial biomass nearly doubled, reaching 47.6 g plant⁻¹ compared to 23.8 g plant⁻¹ in untreated plants under salinity (+100%). Root fresh weight also rose markedly, from 29.6 g plant⁻¹ to 50.3 g plant⁻¹ (+69.8%). Leaf area expanded substantially, averaging 660.8 cm² per plant at T50 versus 301.2 cm² in salinity-stressed controls (+119.4%). Total chlorophyll content increased by 3.9-11.2%, with values rising from 43.43 µg cm⁻² in untreated plants under salinity to a maximum of 48.29 µg cm⁻² at 25 μM melatonin. Stomatal conductance showed a significant improvement as well, reaching 169.4 mmol m⁻² s⁻¹ at T50, which represented a 50.6% increase relative to untreated plants. Biochemical stress indicators declined consistently in melatonin-treated plants. MDA content decreased by 36.2% (from 3.87 to 2.47 nmol mg⁻¹ FW at T50), while foliar proline accumulation was reduced by 28.1% under the same treatment. Leaf total phenol content followed a similar trend, showing reductions ranging from 19.2 to 48.1% across all melatonin doses compared with salt-stressed controls. In most cases, these decreases were statistically significant (P<0.05), indicating improved redox homeostasis and membrane stability under salt stress.

conclusionsAmong the tested concentrations, 50 μM melatonin was the most effective in promoting growth and alleviating stress. These findings highlight its potential as a pre-harvest strategy to enhance basil performance under salinity within the broader context of melatonin-based stress management.