Alkali stress tolerance and the mitigating effect of melatonin on alkali stress in Camelina sativa

To evaluate the alkali tolerance of different genotypes of camelina (Camelina sativa) and the potential use of melatonin to alleviate alkali stress in the plant, the present study was first conducted with 16 different genotypes of camelina under a variety of NaHCO₃ concentrations (0, 5, 10, 20, and 40 mmol·L⁻¹). Camelina seedling length, root length, and chlorophyll content were evaluated. Based on a log-logistic dose-response curve, two camelina genotypes were the most sensitive and tolerant and were further tested in the second experiment for the potential use of melatonin to alleviate alkali stress. The effect of foliar application of 50 μmol·L⁻¹ melatonin on plant height, yield, osmotic regulation, membrane permeability, and fatty acids was studied using the two camelina genotypes. The results showed that the foliar application of 50 μmol·L⁻¹ melatonin effectively alleviated the damage of alkali stress to the plant, and significantly (P < 0.05) increased the plant height, yield, soluble protein content, chlorophyll content, and F_v/F_m. Foliar application of melatonin significantly increased the activity of antioxidant enzymes such as superoxide dismutase and catalase. In summary, foliar application of melatonin shows great potential for alleviating alkali stress in camelina by enhancing photosynthesis efficiency, modulating the activity of antioxidant enzymes, and improving the alkali tolerance of the plant.