Salt stress severely reduces growth and yield of plants. Considering the positive effects of selenium (Se) and chitosan (Cs) separately against abiotic stress, in these experiments, we synthesized chitosan–selenium nanoparticles (Cs–Se NPs) and investigated their ability to reduce the negative effects of salt stress on growth and some biochemical parameters of bitter melon (Momordica charantia). Bitter melon plants were grown at three NaCl salinity levels (0, 50, and 100 mM) and a foliar spray of Cs–Se NPs (0, 10, and 20 mg L−1) was applied. Some key morphological, biochemical, and physiological parameters in leaf samples and essential oil from fruit were measured at harvest. Salinity decreased growth and yield while foliar application of Cs–Se NPs increased these critical parameters. Furthermore, Cs–Se NPs enhanced bitter melon tolerance to salinity by increasing antioxidant enzyme activity, proline concentration, relative water content, and K+, and decreasing MDA and H2O2 oxidants and Na aggregation in plant tissues. Yield was also improved, as the highest amount of essential oils was produced by plants treated with Cs–Se NPs. Generally, the greatest improvement in measured parameters under saline conditions was obtained by treating plants with 20 mg L−1 Cs–Se NPs, which significantly increased salinity tolerance in bitter melon plants.

Priming is one of the seed enhancement methods that might be resulted in increasing seed performance (germination and emergence) under stress conditions such as salinity, temperature and drought stress. The objective of this research was to evaluate the effect of different priming types on seed germination of two medicinal plants including pot marigold (Calendula officinalis) and sweet fennel (Foeniculum vulgare) under salinity stress. Treatments were combinations of 5 levels of salinity stress (0, 2.5, 5, 7.5 and 10 ds m-1) and 5 levels of priming (control, GA 3 , Manitol, NaCl and distilled water) with 3 replications. Seeds of pot marigold and sweet fennel were primed for 24 h at 25°C. Results indicated that with increasing salinity, germination traits such as germination percent, rate and plumule length decreased, but seed priming with GA 3 and NaCl showed lower decrease. In all of the salinity levels, primed seeds (except manitol) possessed more germination rate and plumule length than control. The highest radicle fresh and dry weight in pot marigold was seen at 7.5 ds m-1 salinity stress level. It seems that higher germination rate in pot marigold shows higher tolerance to salinity than sweet fennel. Priming with NaCl and GA 3 caused an increase in germination percent of pot marigold and sweet fennel in various range of salinity, but in lower salinity levels percent of germination was higher than upper ones. The result of this experiment is consistent with the hypothesis that under undesirable conditions such as salinity stress, priming with GA 3 and NaCl can prepare a suitable metabolic reaction in seeds and can improve seed germination performance and seedling establishment.

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Cadmium is one of the most toxic heavy metals among major environmental pollutants. Cd is released into water and soil by humans through urban, industrial, and agricultural activities. Most importantly, contamination by Cd in agriculture happens through long-term use of phosphate fertilizers, contaminated water, and waste water appli

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.