Chitosan-based Schiff base-metal (Fe, Cu, and Zn) complexes mitigate the negative consequences of drought stress on pomegranate fruits.

Drought is one of the major environmental stresses that impairs fruit productivity and quality. The proper management of minerals can, however, assist plant to maintain their growth even under drought incidents, and is considered one of the encouraging approaches to refine the drought tolerance of plants. The beneficial effects of chitosan (CH)-based Schiff base-metal complexes (e.g., CH-Fe, CH-Cu and CH-Zn) in reducing the harmful impacts of different levels of drought stress on the growth and productivity of 'Malase Saveh' pomegranate cultivar were examined. All CH-metal complexes displayed favorable effects on the yield- and growth-related attributes of pomegranate trees cultivated under well-watered and different drought situations, with the best effects were observed with CH-Fe application. Specifically, leaves of CH-Fe-treated pomegranate plants showed higher concentrations of photosynthetic pigments [chlorophyll a (Chl a), Chl b, Chl a+b, and carotenoids by 28.0, 29.5, 28.6 and 85.7%, respectively] and microelements (Fe by 27.3%), along with increased levels of superoxide dismutase (by 35.3%) and ascorbate peroxidase (by 56.0%) enzymatic activities relative to those of CH-Fe-non-treated pomegranate plants under intense drought stress. CH-Fe-treated drought-stressed pomegranate leaves showed high increment of abscisic acid (by 25.1%) and indole-3-acetic acid (by 40.5%) relative to CH-Fe-non-treated pomegranates. The increased contents of total phenolics, ascorbic acid, total anthocyanins, and titratable acidity (by 24.3, 25.8, 9.3 and 30.9%, respectively) in the fruits of CH-Fe-treated drought-stressed pomegranates indicated the advantageousness of CH-Fe on the enhancement of fruit nutritional qualities. Collectively, our results prove the explicit functions of these complexes, particularly CH-Fe, in the control of drought-induced negative effects on pomegranate trees grown in semi-arid and dry areas.

Physiological and Biochemical Responses of Commercial Strawberry Cultivars under Optimal and Drought Stress Conditions.

Improving the extent of adaptation and the choice of the most tolerant cultivar is the first step to mitigating the adverse effects of limited water, especially in susceptible plants such as strawberries. To address this issue, two commercial strawberry cultivars (Camarosa and Gaviota) were compared when irrigated to match 100, 75, 50, and 25% field capacity (FC) to simulate the control, slight, moderate, and severe drought stress conditions, respectively. Drought stress induced the reduction of total chlorophyll, carotenoid, relative water content, and phenolic content significantly, whereas the activity of antioxidant enzymes, electrolyte leakage, osmolyte accumulation, and oxidative markers upsurged progressively in drought severity-dependent behavior. Gaviota produced more proline, hydrogen peroxide as a marker of membrane lipid peroxidation and disposed of by higher electrolyte leakage, significantly. On the other hand, Camarosa having higher soluble carbohydrates as well as enzymatic and non-enzymatic antioxidants could be considered a drought-tolerant cultivar. Genotypic variation between these cultivars could be used in breeding projects to promote drought-tolerant strawberries in the future.

Exogenous melatonin mitigates salinity-induced damage in olive seedlings by modulating ion homeostasis, antioxidant defense, and phytohormone balance.

Melatonin (MEL) is a ubiquitous molecule with pleiotropic roles in plant adaption to stress. In this study, we investigated the effects of foliar spray of 100 and 200 µM MEL on the biochemical and physiological traits linked with the growth performance of olive seedlings exposed to moderate (45 mM NaCl) and severe (90 mM NaCl) salinity. Both salt stress conditions caused a considerable reduction in leaf relative water content and the contents of photosynthetic pigments (carotenoids, chlorophylls a and b, and total chlorophylls), K+ and Ca+2 , while the contents of Na+ and the activities of antioxidant enzymes increased. In addition, salt-stressed olive seedlings showed high accumulations of hydrogen peroxide (H2 O2 ), malondialdehyde (MDA), and electrolyte leakage (EL), indicating that olive seedlings suffered from salinity-induced oxidative damage. In contrast, MEL application revived the growth of olive seedlings, including shoot height, root length and biomass under salt stress conditions. MEL protected the photosynthetic pigments and decreased the Na+ /K+ ratio under both moderate and severe salt stresses. Furthermore, MEL induced the accumulations of proline, total soluble sugars, glycine betaine, abscisic acid, and indole acetic acid in salt-stressed olive seedlings, which showed a positive correlation with improved leaf water status and biomass. MEL application also increased the activities of catalase, superoxide dismutase, ascorbate peroxidase, and peroxidase in salt-stressed seedlings, resulting in lower levels of H2 O2 , MDA, and EL in these plants. Taken together, MEL mitigates salinity through its roles in various biochemical and physiological processes, thereby representing a promising agent for application in crop protection.

Mitigation of the effect of drought on growth and yield of pomegranates by foliar spraying of different sizes of selenium nanoparticles.

BACKGROUND: Drought is a very important environmental stressor, which has negative effects on the growth of trees, decreasing their yield. The role of different-sized selenium nanoparticles (Se-NPs) in the mitigation of environmental stresses such as drought in crops has not yet been investigated. RESULTS: Trees treated with Se-NPs displayed higher levels of photosynthetic pigments, a better nutrient status, better physical parameters (especially fruit cracking) and chemical parameters, a higher phenolic content, and higher concentrations of osmolytes, antioxidant enzymes, and abscisic acid than untreated trees under drought stress. Foliar spraying of 10 and 50 nm Se-NPs alleviated many of the deleterious effects of drought in pomegranate leaves and fruits and this was achieved by reducing stress-induced lipid peroxidation and H2 O2 content by enhancing the activity of antioxidant enzymes. Furthermore, the 10 nm Se-NPs treatment produced more noticeable effects than the treatment with 50 nm Se-NPs. CONCLUSION: Results confirm the positive effects of nanoparticle spraying, especially the role of 10 nm Se-NPs in the management of negative effects of drought not only for pomegranates but potentially also for other crops. © 2021 Society of Chemical Industry.

Melatonin alleviates drought impact on growth and essential oil yield of lemon verbena by enhancing antioxidant responses, mineral balance, and abscisic acid content.

Melatonin has recently emerged as a multifunctional biomolecule with promising aspects in plant stress tolerance. The present study examined the effects of foliar-sprayed melatonin (0, 100, and 200 µM) on growth and essential oil yield attributes of lemon verbena (Lippia citriodora) under water-shortage (mild, moderate and severe). Results revealed that melatonin minimized drought effects on lemon verbena, resulting in improved growth and essential oils yield. Drought impositions gradually and significantly reduced several growth parameters, such as plant height and biomass, whereas melatonin application revived the growth performance of lemon verbena. Melatonin protected the photosynthetic pigments and helped maintain the mineral balance at all levels of drought. Melatonin stimulated the accumulation of proline, soluble sugars and abscisic acid, which were positively correlated with a better preservation of leaf water status in drought-stressed plants. Melatonin also prevented oxidative damages by enhancing the superoxide dismutase, ascorbate peroxidase and catalase activities. Furthermore, increased levels of total phenolic compounds, chicoric acid, caffeic acid and chlorogenic acid, as well as ascorbate and total antioxidant capacity in melatonin-sprayed drought-stressed plants indicated that melatonin helped verbena plants to sustain antioxidant and medicinal properties during drought. Finally, melatonin treatments upheld the concentrations and yield of essential oils in the leaves of lemon verbena regardless of drought severities. These results provided new insights into melatonin-mediated drought tolerance in lemon verbena, and this strategy could be implemented for the successful cultivation of lemon verbena, and perhaps other medicinal plants, in drought-prone areas worldwide.

Association analysis and molecular tagging of phytochemicals in the endangered medicinal plant licorice (Glycyrrhiza glabra L.).

Licorice (Glycyrrhiza glabra L.) is a medicinal plant species valued in many countries in Asia and Europe for its phytochemical characteristics. Licorice biodiversity is becoming threatened nowadays in Iran due to increasing demand and a drastic decline of its natural habitats. Therefore, licorice domestication would be necessary in the near future, and molecular breeding would help to introduce genotypes suitable for cultivation. The present study was carried out with 170 individual licorice plants sampled in the wild in 59 localizations in 21 provinces of Iran. The association of 436 polymorphic AFLP markers, produced by 15 primer combinations (EcoRI/MseI), with six phenotypic phytochemical traits was studied. The AMOVA analysis show gene diversity among and within localizations. The population structure analysis identified two main sub-populations with significant genetic variation. Significant associations were identified between three markers (E3/M40-4, E34/M4-12 and E12/M31-15) and glycyrrhizin concentration, and between four markers (E11/M34-12, E11/M34-15, E9/M7-29, and E9/M7-30) and phenolic compounds contents. Markers detected can be useful in the domestication of licorice as well as in breeding programs. Licorice sampled in four localizations (KBA1, KBA2, SKh2 and Fa1) were found to be superior in terms of glycyrrhizin and antioxidants content, and therefore they can be considered as elite genotypes which could be included in the domestication process.

Melatonin foliar sprays elicit salinity stress tolerance and enhance fruit yield and quality in strawberry (Fragaria × ananassa Duch.).

The increasing salinity in soils and irrigation water is a major concern for growers of strawberry, a salt-sensitive horticultural crop. The hormone melatonin (N-acetyl-5-methoxytryptamine) is involved in many biological processes and affects plant responses to environmental stresses. The effects of weekly 100 and 200 µM melatonin sprays on leaf composition parameters (photosynthetic pigment and macronutrient concentrations, oxidative stress markers, antioxidant defense systems and abscisic acid concentrations), fruit yield and quality parameters (soluble solids, total acidity, ascorbic acid, total antioxidants and phenolics and sugars), and leaf and fruit melatonin have been studied in strawberry grown under non-saline, moderate and intense salinity conditions (0, 40 and 80 mM NaCl, respectively). Salinity led to decreases in yield, fruit quality parameters and leaf photosynthetic pigments and macronutrient concentrations, as well as to increases in oxidative stress, with melatonin foliar application alleviating all these changes. On the other hand, salinity led to increases in the leaf levels of antioxidant enzymes, abscisic acid and melatonin, with foliar applications of melatonin boosting those increases. In the absence of salinity stress, melatonin led to smaller changes in all parameters in the same direction to that observed in the presence of salinity. Furthermore, melatonin resulted in increases in strawberry fruit yield and quality, especially in plants grown under salinity. Results indicate that the effects of melatonin application are associated with a boost in leaf antioxidant enzymes and abscisic acid, and support that the application of melatonin is a promising tool for mitigating salt stress in strawberry.

Alleviation of the effect of salinity on growth and yield of strawberry by foliar spray of selenium-nanoparticles.

The present study investigated the beneficial role of selenium-nanoparticles (Se-NPs) in mitigating the adverse effects of soil-salinity on growth and yield of strawberry (Fragaria × ananassa Duch.) plants by maneuvering physiological and biochemical mechanisms. The foliar spray of Se-NPs (10 and 20 mg L-1) improved the growth and yield parameters of strawberry plants grown on non-saline and different saline soils (0, 25, 50 and 75 mM NaCl), which was attributed to their ability to protect photosynthetic pigments. Se-NPs-treated strawberry plants exhibited higher levels of key osmolytes, including total soluble carbohydrates and free proline, compared with untreated plants under saline conditions. Foliar application of Se-NPs improved salinity tolerance in strawberry by reducing stress-induced lipid peroxidation and H2O2 content through enhancing activities of antioxidant enzymes like superoxide dismutase and peroxidase. Additionally, Se-NPs-treated strawberry plants showed accumulation of indole-3-acetic acid and abscisic acid, the vital stress signaling molecules, which are involved in regulating different morphological, physiological and molecular responses of plants to salinity. Moreover, the enhanced levels of organic acids (e.g., malic, citric and succinic acids) and sugars (e.g., glucose, fructose and sucrose) in the fruits of Se-NPs-treated strawberry plants under saline conditions indicated the positive impacts of Se-NPs on the improvement of fruit quality and nutritional values. Our results collectively demonstrate the definite roles of Se-NPs in management of soil salinity-induced adverse effects on not only strawberry plants but also other crops.

Effects of postharvest polyamine application and edible coating on maintaining quality of mango (Mangifera indica L.) cv. Langra during cold storage.

Mango is a tropical fruit which is sensitive to chilling injury. The present work investigated the potential of edible coatings of chitosan and polyamine spermidine in increasing shelf life and quality of mango. The control fruits (treated with distilled water) and the mango fruits treated with different concentrations of chitosan (0.5%, 1.0%, and 2.0%) and spermidine (0.5, 1.0, and 2.0 mM) were studied to improve postharvest characteristics and quality maintenance during cold storage. Parameters such as firmness, weight loss, fungal contamination, total phenol, antioxidant activity, vitamin C, pH, total soluble solids (TSS), titratable acidity (TA), flavor index, color index, and ethylene production were measured after at harvest (0), 8, 16, and 24 days of storage at 15 ± 2°C and relative humidity of 85%-90%. Chitosan and spermidine delayed water loss, firmness, and fungal contamination. Application of chitosan containing ascorbic acid significantly increased phenolic content and antioxidant activity compared to the control plants. It also changed soluble solid content, TA, pH of pulp, and sugar content and decreased ethylene production. The obtained results suggested that chitosan (2%) and spermidine (2 mM) had potential to improve firmness and delay deterioration processes of "Langra" mango after harvest.

Comparison the effect of putrescine application on postharvest quality of Pyrus communis cv. "Shah-Miveh" and "Spadona".

Role of putrescine for extending storage life of pear cv. "Shah-Miveh" and "Spadona" was evaluated. The trees were sprayed by various concentrations of putrescine (0.5, 1, and 2 mM) and distilled water "control." After harvest, all samples were stored at 0 ± 1°C, 80%-85% RH for 21 weeks. Thereafter, some physico-chemical attributes were measured initially and after each storage period 7, 14, and 21 weeks. Putrescine at 1 and 2 mM reduced fruit softening, weight loss, color changes (L*, hue angle), fungal infection as well as retarded the degradation of total soluble solids, titratable acidity, ascorbic acid, total phenol (TP), and total antioxidant activity (TAA). However, fruit softening, weight loss, and hue angle rates were slower in "Shah-Miveh" to "Spadona." Moreover, at the end of storage, "Shah-Miveh" demonstrated more TP and TAA in compare to "Spadona." Thus, putrescine application at higher values may be an effective tool to prolong pear postharvest life during storage.

Effect of drought stress on growth parameters, osmolyte contents, antioxidant enzymes and glycyrrhizin synthesis in licorice (Glycyrrhiza glabra L.) grown in the field.

Glycyrrhiza glabra L. (licorice) is a medicinal species rich in the specialised plant metabolite glycyrrhizin. It has been previously proposed that drought, which is increasing in importance due to the climatic change and scarcity of water resources, can promote the synthesis of glycyrrhizin. The effects of slight, moderate and intense drought (70, 35 and 23% of the regular irrigation, respectively) on growth parameters, osmolyte content, oxidative stress markers, antioxidant enzymes, glycyrrhizin biosynthesis genes and root glycyrrhizin concentration and contents, have been assessed in five Iranian licorice genotypes grown in the field. Drought decreased progressively biomass and leaf relative water contents, and increased progressively osmolyte (proline, glycine-betaine and soluble sugars) concentrations in leaves and roots. Drought caused oxidative stress in leaves, as indicated by lipid peroxidation and hydrogen peroxide concentrations, and increased the activities of antioxidant enzymes in leaf extracts (catalase, peroxidase, superoxide dismutase and pholyphenoloxidase). Drought promoted the synthesis of glycyrrhizin, as indicated by the increases in the expression of the glycyrrhizin biosynthesis pathway genes SQS1, SQS2, bAS, CYP88D6, CYP72A154 and UGT73, and increased the root concentrations of glycyrrhizin with drought in some genotypes. However, the large decreases in root biomass caused by drought led to general decreases in the amount of glycyrrhizin per plant with moderate and intense drought, whereas the slight drought treatment led to significant decreases in glycyrrhizin content in only one genotype. Under intense drought two of the genotypes were still capable to maintain half of the control glycyrrhizin yield, whereas in the other three genotypes glycyrrhizin yield was 22-33% of the control values. Results indicate that under intense drought, with only 23% of the normal water dose being applied, an appropriate choice of genotype can still lead to acceptable glycyrrhizin yields.

Effects of postharvest treatments with chitosan and putrescine to maintain quality and extend shelf-life of two banana cultivars.

Chitosan (1.0% and 2.0%) and putrescine (1.0 and 2.0 mmol/L) treatments were used to investigate the effects of these compounds on the postharvest quality and shelf-life of two banana cultivars, "Native" and "Cavendish." Fruits were stored at 15 ± 2°C and a relative humidity of 85%-90% during a 20-day period. In the controls, increases in weight loss, microbial population, total soluble solids, and ethylene production and decreases in firmness, ascorbic acid contents, and fruit lightness occurred gradually during storage. All these changes were delayed significantly after treatments with chitosan and putrescine. Application of putrescine and chitosan also caused small increases in phenolic compound contents and antioxidant activity at the end of the storage period. Results obtained suggest that a treatment with 1% chitosan is effective in improving the postharvest quality and shelf-life of banana, and open the possibility that lower concentrations of chitosan may be also effective.