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Abstract Background Melatonin is a multi-functional molecule widely employed in order to mitigate abiotic stress factors, in general and salt stress in particular. Even though previous reports revealed that melatonin could exhibit roles in promoting seed germination and protecting plants during various developmental stages of several plant species under salt stress, no reports are available with respect to the regulatory acts of melatonin on the physiological and biochemical status as well as the expression levels of defense- and secondary metabolism-related related transcripts in bitter melon subjected to the salt stress. Results Herewith the present study, we performed a comprehensive analysis of the physiological and ion balance, antioxidant system, as well as transcript analysis of defense-related genes (WRKY1, SOS1, PM H + -ATPase, SKOR, Mc5PTase7, and SOAR1) and secondary metabolism-related gene expression (MAP30, α-MMC, polypeptide-P, and PAL) in salt-stressed bitter melon (Momordica charantia L.) plants in response to melatonin treatment. In this regard, different levels of melatonin (0, 75 and 150 µM) were applied to mitigate salinity stress (0, 50 and 100 mM NaCl) in bitter melon. Accordingly, present findings revealed that 100 mM salinity stress decreased growth and photosynthesis parameters (SPAD, Fv/Fo, Y(II)), RWC, and some nutrient elements (K+, Ca2+, and P), while it increased Y(NO), Y(NPQ), proline, Na+, Cl−, H2O2, MDA, antioxidant enzyme activity, and lead to the induction of the examined genes. However, prsiming with 150 µM melatonin increased SPAD, Fv/Fo, Y(II)), RWC, and K+, Ca2+, and P concentration while decreased Y(NO), Y(NPQ), Na+, Cl−, H2O2, and MDA under salt stress. In addition, the antioxidant system and gene expression levels were increased by melatonin (150 µM). Conclusions Overall, it can be postulated that the application of melatonin (150 µM) has effective roles in alleviating the adverse impacts of salinity through critical modifications in plant metabolism.

Abstract Background Salinity is an important global problem with destructive impacts on plants leading to different biochemical and metabolic changes in plants through induced oxidative stress that disturbs metabolism, growth, performance and productivity of plants. Given that putrescine (Put) and carbon quantum dots (CQDs), individually, have promising effects in different plant processes, the idea of their combination in a nano-structure “Put-CQD” lead to its synthesis to evaluate the potential exertion of synergistic effects. The current study aimed to investigate the application of newly-synthesized nanoparticles (NPs) consisting of CQDs and Put in grapevine (Vitis vinifera cv. ‘Sultana’) under salinity stress conditions. For this purpose, Put, CQDs and Put-CQD NPs at 5 and 10 mg L− 1 concentrations were applied as chemical priming agents in ‘Sultana’ grapevine 48 h prior salinity stress imposition (0 and 100 mM NaCl). Results Salinity significantly decreased (P ≤ 0.05) morphological parameters, photosynthetic pigments, chlorophyll fluorescence parameters and membrane stability index. In addition, salinity enhanced MDA, H2O2, proline content and antioxidant enzyme activity. Results revealed that Put-CQD NPs, particularly at 10 mg L− 1 concentration, alleviated the destructive impacts of salinity stress by improving leaf fresh and dry weights, K+ content, photosynthetic pigments, chlorophyll fluorescence and SPAD parameters, proline content, total phenolics and antioxidant enzymatic activities (CAT, APX, GP and SOD), while decreasing Na+ content, EL, MDA and H2O2 levels. Conclusion To conclude, Put-CQD NPs represent an innovative priming treatment that could be effectively applied on grapevine to improve plant performance under salinity stress conditions.

Plant growth and development are adversely affected by salinity. In order to evaluate the effects of different salinity levels and application of chitosan on some growth parameters, photosynthesis pigments and essential oils content and yield of moldavian balm (Dracocephalium moldavica L.), a greenhouse experiment was carried out as a factorial based on the completely randomized design (CRD) and three replications. The first factor was three levels of salinity stress included 0, 25 and 50 Mm NaCl and the second factor was application of chitosan (0, 0.25, 0.5 and 1 % w/v). The studied traits include the morphological (plant height, shoot fresh and dry weight, leaf fresh and dry weight and inflorescence length), chlorophyll fluorescence (Variable fluorescence, maximum chlorophyll fluorescence yield, Water degradation complex), photosynthesis pigments (chlorophyll a and b, carotenoid) and also essential oil content and yield. The results demonstrated that all morphological traits and some of physiological characteristics including chlorophyll fluorescence indices, chlorophyll a, and chlorophyll b and carotenoid contents significantly decreased with increasing the salinity level. In addition, the results showed that with application of chitosan in the salinity conditions, all morphological traits, antioxidant enzymes activity, and chlorophyll fluorescence (Variable fluorescence, maximum chlorophyll fluorescence yield, Water degradation complex, Y (II)) parameters improved compared with control. Furthermore, foliar application of chitosan increased the essential oil and yield under salinity stress condition. It seems that chitosan has a positive effect to overcome effects of salinity stress and might be help to increasers essential oil yield on medicinal plants.

Salinity stress is one of the most destructive stress factors causing adverse impacts on growth and productivity of crops plants. In order to combat or to make crop plants compatible with salinity stress, many attempts have been made to alleviate the devastating impacts of salinity stress on plants. Of those attempts, engineered nano-particles (NPs) have gained great interest in recent years, having been tested in a number of crop plants; however, they remain to be investigated for medicinal and aromatic plants. For that reason, the interaction effects of cerium oxide NPs (CeO2 NPs at 25, 50 and 100 mg L−1) and salinity stress (50 and 100 mM NaCl) on Moldavian balm (Dracocephalum moldavica L.) was evaluated. Salinity significantly decreased agronomic traits such as leaf and shoot fresh and dry weight, photosynthetic pigment content and SPAD, whereas it increased MDA, H2O2 and proline (Pro) content, electrolyte leakage (EL) and antioxidant enzymatic activities (SOD, APX and GP). However, CeO2-NP treatments enhanced growth performance of the plants exposed under salinity stress by improving agronomic traits, photosynthetic pigment content, SPAD, Pro, and antioxidant enzymes. Furthermore, CeO2-NPs caused a decrease in MDA, H2O2 and EL via higher antioxidant enzymatic activity under salinity conditions. Of the concentrations of CeO2-NPs tested, 50 mg L−1 concentration gave the best results under both non-stress and salt-stress conditions. In conclusion, foliar spray of CeO2-NP treatments in Moldavian balm improved plant performance under salinity and may be considered as a promising treatment in alleviating the effects of salt stress.