Effect of melatonin foliar sprays on morphophysiological attributes, fruit yield and quality of Momordica charantia L. under salinity stress.

Soil salinity is one of the increasing problems in agricultural fields in many parts of the world, adversely affecting the performance and health of the plants. As a pleiotropic signal and antioxidant molecule in both animals and plants, melatonin has been reported to possess significant roles in combating with stress factors, in general and salt stress, in particular. In this study, the interactive effects of melatonin (0, 75, and 150 µM) and salt stress (0, 50 and 100 mM NaCl) were investigated by assaying the some agronomic, physlogical and biochemical attributes and essential oil compounds of bitter melon (Momordica charantia). The results showed that exogenous melatonin could promote net photosynthetic rate (Pn) and PSII efficiency (Fv/Fm), increase K+ content and activity of antioxidant enzymes and decrease reactive oxygen species, malondialdehyde and Na+ content in stress-submitted seedlings, in comparison to the non-stressed seedlings (p < 0.05). Melatonin increased content of essential oils. Concerning the major compounds of fruits of bitter melon, charantin, momordicin and cucurbitacin were increased with the melatonin treatments, whereas they were critically decreased with the salt stress. In addition, melatonin increased the antioxidant capacity in fruits under non-saline and salinity conditions. Amid the concentrations of melatonin, plants treated with 150 µM of melatonin under either non-saline or saline conditions showed better performance and productivity. Therefore, application of 150 µM melatonin resulted in a significant improvement of salinity tolerance and essential oil compounds in bitter melon plant, suggesting this as an efficient 'green' strategy for sustainable crop production under salt stress conditions.

Seedling nanopriming with selenium-chitosan nanoparticles mitigates the adverse effects of salt stress by inducing multiple defence pathways in bitter melon plants.

Advances in the nanotechnology fields provided crucial applications in plant sciences, contributing to the plant performance and health under stress and stress-free conditions. Amid the applications, selenium (Se), chitosan and their conjugated forms as nanoparticles (Se-CS NPs) have been revealed to have potential of alleviating the harmful effects of the stress on several crops and subsequently enhancing the growth and productivity. The present study was addressed to assay the potential effects of Se-CS NPs in reversing or buffering the harmful effects of salt stress on growth, photosynthesis, nutrient concentration, antioxidant system and defence transcript levels in bitter melon )Momordica charantia(. In addition, some secondary metabolite-related genes were explicitly examined. In this regard, the transcriptional levels of WRKY1, SOS1, PM H+-ATPase, SKOR, Mc5PTase7, SOAR1, MAP30, α-MMC, polypeptide-P and PAL were quantified. Our results demonstrated that Se-CS NPs increased growth parameters, photosynthesis parameters (SPAD, Fv/Fm, Y(II)), antioxidant enzymatic activity (POD, SOD, CAT) and nutrient homeostasis (Na+/K+, Ca2+, and Cl-) and induced the expression of genes in bitter melon plants under salt stress (p ≤ 0.05). Therefore, applying Se-CS NPs might be a simple and effective way of improving crop plants' overall health and yield under salt stress conditions.