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.

Antioxidant Compounds of Potato Breeding Genotypes and Commercial Cultivars with Yellow, Light Yellow, and White Flesh in Iran.

Potatoes are a staple food with high antioxidant properties that can positively affect population health. The beneficial effects of potatoes have been attributed to tuber quality. However, the tuber quality related researches at genetic levels are very few. Sexual hybridization is a powerful strategy for producing new and valuable genotypes with high quality. In this study, 42 breeding potato genotypes in Iran were selected based on appearance characteristics such as shape, size, color, eyes of tubers, and tuber yield and marketability. The tubers were evaluated for their nutritional value and properties, viz. phenolic content, flavonoids, carotenoids, vitamins, sugars, proteins, and antioxidant activity. Potato tubers with white flesh and colored skin had significantly higher levels of ascorbic acid and total sugar. The result showed that higher phenolic, flavonoid, carotenoid, protein concentration, and antioxidant activity were noted in yellow-fleshed. Burren (yellow-fleshed) tubers had more antioxidant capacity in comparison to genotypes and cultivars, which did not differ significantly with genotypes 58, 68, 67 (light yellow), 26, 22, and 12 (white). The highest correlation coefficients in antioxidant compounds were related to total phenol content and FRAP, suggesting that phenolics might be crucial predictors of antioxidant activities. The concentration of antioxidant compounds in the breeding genotypes was higher than in some commercial cultivars, and higher antioxidant compounds content and activity were detected in yellow-fleshed cultivars. Based on current results, understanding the relationship between antioxidant compounds and the antioxidant activity of potatoes could be very helpful in potato breeding projects.

Exogenous melatonin increases salt tolerance in bitter melon by regulating ionic balance, antioxidant system and secondary metabolism-related genes.

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.

Salt Stress Mitigation via the Foliar Application of Chitosan-Functionalized Selenium and Anatase Titanium Dioxide Nanoparticles in Stevia (Stevia rebaudiana Bertoni).

High salt levels are one of the significant and major limiting factors on crop yield and productivity. Out of the available attempts made against high salt levels, engineered nanoparticles (NPs) have been widely employed and considered as effective strategies in this regard. Of these NPs, titanium dioxide nanoparticles (TiO2 NPs) and selenium functionalized using chitosan nanoparticles (Cs-Se NPs) were applied for a quite number of plants, but their potential roles for alleviating the adverse effects of salinity on stevia remains unclear. Stevia (Stevia rebaudiana Bertoni) is one of the reputed medicinal plants due to their diterpenoid steviol glycosides (stevioside and rebaudioside A). For this reason, the current study was designed to investigate the potential of TiO2 NPs (0, 100 and 200 mg L-1) and Cs-Se NPs (0, 10 and 20 mg L-1) to alleviate salt stress (0, 50 and 100 mM NaCl) in stevia. The findings of the study revealed that salinity decreased the growth and photosynthetic traits but resulted in substantial cell damage through increasing H2O2 and MDA content, as well as electrolyte leakage (EL). However, the application of TiO2 NPs (100 mg L-1) and Cs-Se NPs (20 mg L-1) increased the growth, photosynthetic performance and activity of antioxidant enzymes, and decreased the contents of H2O2, MDA and EL under the saline conditions. In addition to the enhanced growth and physiological performance of the plant, the essential oil content was also increased with the treatments of TiO2 (100 mg L-1) and Cs-Se NPs (20 mg L-1). In addition, the tested NPs treatments increased the concentration of stevioside (in the non-saline condition and under salinity stress) and rebaudioside A (under the salinity conditions) in stevia plants. Overall, the current findings suggest that especially 100 mg L-1 TiO2 NPs and 20 mg L-1 Cs-Se could be considered as promising agents in combating high levels of salinity in the case of stevia.

Chitosan-Selenium Nanoparticle (Cs-Se NP) Foliar Spray Alleviates Salt Stress in Bitter Melon.

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.

Effect of foliar application of selenium on morphological and physiological indices of savory (Satureja hortensis) under cadmium stress.

Cadmium is a heavy metal that pollutes the environment and affects plants physiologically and morphologically. Selenium is considered as a beneficial element, with effective roles in increasing plant tolerance to environmental stresses. A greenhouse factorial pot experiment was conducted to study the impact of selenium on traits of Savory plants under Cd stress. Experimental factors included soil contamination with cadmium (0, 75, 100, and 150 µM) and foliar spraying of selenium (0, 10, 20, and 40 µM of Sodium Selenate). Biomass, photosynthetic pigments including chlorophyll a, chlorophyll b, total chlorophyll, proline, total soluble solids, cell membrane leakage, relative water content of leaves antioxidant enzymes, and Cd and Zn concentration in shoot and root were recorded. Results revealed that Cd stress decreased vegetative growth criteria, photosynthetic pigments include chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid almost, 55%, 57%, 57%, and 68%, respectively, while poline, cell membrane leakage, peroxidase (POD), and catalase (CAT) antioxidant enzymes were increased with increasing Cd concentrations. Foliar spray of selenium reduced the toxic effects of Cd stress on savory plants via enhancing of proline content and stimulation of CAT and POD enzymes and limitation of cell membrane leakage. Also, selenium foliar spray improved chlorophyll content under Cd stress condition and decreased cadmium accumulation 29% in root, respectively. In general, these results suggest that foliar application of selenium could mitigate Cd toxicity and improve growth and antioxidant capacity of savory under different level of cadmium heavy metal stress.

Ameliorative effects of ascorbic acid on tolerance to drought stress on pepper (Capsicum annuum L) plants.

Drought stress is an important environmental stress that clearly affect biological systems of plants. There is a possibility that growth regulators are able to protect plants under drought conditions. Ascorbic acid (AsA) plays a particular role on growth of plants and protects cells from oxidative damage caused by environmental stresses. This study emphasized the impacts of AsA on improving the drought tolerance of the pepper plants. Based on a factorial arrangement in a completely randomized design, the experiment had two factors. The first factor was drought: irrigation within the field capacity, moderate stress (irrigation within the 60% field capacity) and severe stress (irrigation within the 30% field capacity). The second factor was AsA: 0 mM sprayed with distilled water, 0.5 mM and 1 mM. The experiment had three replications. Drought stress inhibited plant growth parameters including fruit number, height, weight, yield, chlorophyll a and b, total chlorophyll, carotenoid contents, it caused improvement in activity of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), proline content, anthocyanins, soluble sugars, malondialdehyde (MDA) and H2O2 in the leaves of sweet pepper. Application of AsA contributes to an increase in antioxidant enzymes activity such as SOD, CAT, POD and proline contents, chlorophyll a and b, total chlorophyll, carotenoids, soluble carbohydrates. However, it reduced the content of anthocyanins, MDA and H2O2. Based on this study, it can be suggested that ascorbic acid adjusted antioxidant activity, especially after it has been subjected to drought stress.