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Water resources pose a considerable limitation in arid and semi-arid regions like Iran, primarily due to the scarcity of rainfall and heightened evaporation rates. Within open hydroponic systems, a significant concern arises from the depletion of nutrient solutions utilized for crop fertigation. This predicament subsequently gives rise to environmental issues of note and a discernible surge in production expenses. Application of humic acid (HA), as a plant biostimulant, enhances plant tolerance to reduced water supply and counterbalances the effects of diluted nutrient solutions. A greenhouse experiment was conducted to investigate the impact of applying HA (600 ppm) in conjunction with three nutrient solution concentrations (complete nutrient solution (NSc), 75% NSc (NS1), and 50% NSc (NS2)), as well as two irrigation levels (100 and 50% of plant water requirement, IL100 and IL50, respectively). The treatment under IL50 was referred to as ½ NSc, ½ NS1, and ½ NS2. The findings showed that almost all of the traits studied were significantly affected by the applied treatments. The highest yield (409.4 g m−2), leaf area (34.67 cm−2 plant), biomass (1.092 g−1 plant), membrane stability index (90.47%), chlorophyll a (0.99 mg g−1 FW), chlorophyll b (0.413 mg g−1 FW), total chlorophyll (1.54 mg g−1 FW), carotenoid (0.437 mg g−1 FW), vitamin C (730.7 mg ascorbic acid kg−1 FW), amino acid (236.8 µg g−1 FW) and nitrate reductase activity (102.8 µg NO2- mg Protein−1 h−1) were observed in NSc + HA. In addition, the highest carbohydrate (46.99 mg g−1 FW), phenol (1129 mg GAE Kg−1 FW), and flavonoid content (1133 mg Catechin Kg−1 FW) and antioxidant activity (74.75%) were observed in ½ NS1 + HA. In addition, the highest relative water content (86.62%) and nitrate content (1106 mg kg−1 FW) were recorded in NS2 + HA and NSc, respectively. The application of HA combined with different concentrations of the nutrient solution under both irrigation levels caused an increase in most of the parameters studied in rocket plants compared to respective treatments without HA application. In addition, the results obtained confirmed that HA could compensate for the stress caused by a shortage of nutrients and water in the nutrient solution in this crop. [ABSTRACT FROM AUTHOR]

Belonging to the Brassicaceae family, rocket (Eruca sativa (Mill.) Thell.), is considered to be a nitrate-accumulating leafy vegetable. Many studies show that light-emitting diode (LED) lights can be a suitable tool to decrease anti-nutritional compounds (e.g., nitrate (and enhance antioxidant and nutritional quality for phytochemical-rich vegetable production. The positive influence of humic acid on health-promoting compounds in different crops is also well documented. This study aimed to investigate the effects of supplemental LED lights of various spectral compositions, namely 25–100% red, 25–100% blue, and 100% white, as well as their combination with humic acid on the physiological and biochemical responses of rocket plants. ANOVA results showed that almost all the measured traits were significantly affected by LED and humic acid treatments. Generally, LED combined with humic acid improved the accumulation of nutritional compounds (e.g., polyphenols, flavonoid, ascorbic acid, carbohydrate, tannin), increased the activity of key enzymes involved in nitrogen metabolism (e.g., nitrate reductase, nitrite reductase, and glutamine synthetase), and lowered nitrate and ammonium concentrations. The results of principal component analysis indicated that the combination of LED lights, regardless of the spectra, with humic acid was the most effective treatment to enhance the nutritional value and activity of enzymes involved in nitrate assimilation. In sum, these findings may be used as a reference in rocket production for supplemental LED light optimization and its combination with humic acid. • Light-emitting diodes (LED) + humic acid (HA) reduced NO 3 − content in rocket plants. • Plants grown under LED + HA had remarkably higher NR, NiR, and GS enzyme activities. • Concentrations of plant phytochemicals increased under LED with or without HA. [ABSTRACT FROM AUTHOR]

Salinity is one of the most severe environmental stresses limiting agricultural crop production worldwide. Photosynthesis is one of the main biochemical processes getting affected by such stress conditions. Here we investigated the stomatal and non-stomatal factors during photosynthesis in two Iranian melon genotypes "Ghobadlu" and "Suski-e-Sabz", as well as the "Galia" F1 cultivar, with an insight into better understanding the physiological mechanisms involved in the response of melon plants to increasing salinity. After plants were established in the greenhouse, they were supplied with nutrient solutions containing three salinity levels (0, 50, or 100 mM NaCl) for 15 and 30 days. With increasing salinity, almost all of the measured traits (e.g. stomatal conductance, transpiration rate, internal to ambient CO 2 concentration ratio (C i /C a), Rubisco and nitrate reductase activity, carbon isotope discrimination (Δ13C), chlorophyll content, relative water content (RWC), etc.) significantly decreased after 15 and 30 days of treatments. In contrast, the overall mean of water use efficiency (intrinsic and instantaneous WUE), leaf abscisic acid (ABA) and flavonol contents, as well as osmotic potential (Ψ S), all increased remarkably with increasing stress, across all genotypes. In addition, notable correlations were found between Δ13C and leaf gas exchange parameters as well as most of the measured traits (e.g. leaf area, biomass, RWC, Ψ S , etc.), encouraging the possibility of using Δ13C as an important proxy for indirect selection of melon genotypes with higher photosynthetic capacity and higher salinity tolerance. The overall results suggest that both stomatal and non-stomatal limitations play an important role in reduced photosynthesis rate in melon genotypes studied under NaCl stress. This conclusion is supported by the concurrently increased resistance to CO 2 diffusion, and lower Rubisco activity under NaCl treatments at the two sampling dates, and this was revealed by the appearance of lower C i /C a ratios and lower Δ13C in the leaves of salt-treated plants. • DUALEX, an optical sensor, could be applied to assess crop nitrogen status of melon genotypes under salinity condition. • Both the NR and Rubisco activities were significantly reduced under NaCl stress. • A significant positive relationship was observed between Δ13C and C i /C a measured by gas exchanges in all genotypes. • Δ13C was negatively correlated with WUE and WUE i in both sampling times. • Using Δ13C would be an important proxy for selection of melon genotypes with higher photosynthetic performance. [ABSTRACT FROM AUTHOR]

Melon ( Cucumis melo L.) is one of the most important horticultural crops in Iran often cultivated in arid and semiarid regions of the country with salinity problems. The objective of this work was to better understand the mechanisms of physiological and biochemical responses to salinity stress of five Iranian melon landraces “Samsuri”, “Kashan”, “Khatouni”, “Suski-e-Sabz”, and “Ghobadlu” from different geographical origins, and “Galia” F1 cultivar. Plants were grown under greenhouse conditions and irrigated with half-strength Hoagland solution containing 0, 30, 60, or 90 mM NaCl for 60 days. Increase in the external salt concentration was accompanied by an obvious depression in leaf relative water content, membrane stability index, chlorophyll a and b and carotenoid contents, stomata and trichome density, leaf area, specific leaf area, biomass, leaf and stem K + concentrations as well as leaf and stem K + /Na + ratios in all landraces studied. In contrast, hydrogen peroxide, lipid peroxidation, proline and soluble carbohydrate contents, activity of antioxidant enzymes as well as leaf and stem Na + and Cl − concentrations, all increased significantly with increasing stress over all plants. Moreover, carbon isotope discrimination (Δ 13 C), determined on leaf organic matter, was found to be associated with evaluated traits. For example, a highly positive correlation between Δ 13 C and both biomass production and salt tolerance index was notable when all saline treatments were averaged (r = 0.998 and 0.998, respectively). Also, scatter plot and clustering analysis showed that “Suski-e-Sabz” and “Ghobadlu” were placed close to “Galia” F1, a salt tolerant cultivar, indicating that their similar behavior under salinity. Overall, the present results indicated a significant genetic variability for most of the traits studied, suggesting that “Suski-e-Sabz” and “Ghobadlu” could be introduced as the superior landraces and the most promising tolerant parents in the future melon breeding programs due to their suitable performance, in terms of responses to salt stress as compared with other landraces. Also, Δ 13 C can be used as a powerful criterion in melon breeding programs aimed at selection of salt tolerant landraces. [ABSTRACT FROM AUTHOR]

Although salt stress affects all growth stages of a plant, seed germination and seedling growth stages are known to be more sensitive for most plant species. The current research was carried out to find the most effective indicators when screening melons for salt tolerance. For this purpose, a factorial experiment as a completely randomized design was performed in order to investigate the effects of salinity (0, 20, 40, 60 and 80 mM NaCl) on seed germination parameters, hydrogen peroxide content, lipid peroxidation and some antioxidant enzymes (guaiacol peroxidase, ascorbate peroxidase and superoxide dismutase) in five Iranian melon landraces and one melon cultivar 'Galia' F1 at early seedling growth stage. The 'Galia' F1 was included for comparison as a salt-tolerant cultivar. The data collected from all salinity treatments across six landraces were used for analysis of variance and principal component analysis (PCA) using SPSS software as well as for obtaining Pearson's correlation coefficients (r) among all physiological parameters. Obtained results indicated that averaged all landraces across all treatments, increased NaCl significantly affected all the parameters measured. In all landraces, salt tolerance index (STI) decreased as the salt concentrations increased. The principal component analysis revealed variations among the traits and determined four main factors that explained 97.53% of the total variance. Simple correlation coefficient analyses showed the existence of significant positive and negative correlations among characteristics. Our study suggests that the salt tolerance index and principal component analysis can be used as accurate and easy indicators when screening melons for salt tolerance. [ABSTRACT FROM AUTHOR]

Abstract: An evaluation of genetic diversity in 39 wild asparagus populations was carried out using morphological and RAPD markers. A combination of morphological traits and random RAPD primers was used to examine the level of genetic variation and polymorphisms among the populations. A factor analysis using Ward''s method on mean values of morphological characteristics indicated seven main factors resulting in four groups. Analysis of polymorphic bands using Jaccard''s similarity coefficient indicated that genetic similarity ranged between 0.71 and 0.29. At a similarity level of 0.64, the populations were divided in three sub-clusters, containing 34, four and one populations, respectively. Significant regression associations were found between 21 morphological characteristics and 18 RAPD markers, revealing some informative markers associated with some traits. The highest R 2 was related to 18 RAPD markers associated with gender (53.5%) that among them BA-042000 had a maximum R 2. The results showed that Iranian wild asparagus with its high levels of genetic variation could be considered as a valuable gene pool for future asparagus breeding programs. Furthermore, it could be inferred that morphological characteristics and RAPD markers are suitable tools to discriminate asparagus populations for the evaluation of genetic diversity. [Copyright &y& Elsevier]

Arid and semiarid regions with rain shortage and scarce good quality water must make use of low-quality water for irrigation. Consequently, improved plant cultivars for use in these areas should show adaptation capacities to confer drought and salt resistance and allow the cultivation under limited water availabiltiy. The present study was conducted to determine the effect of deficit irrigation with saline water on two local barley landraces, "Karkeni" and "Bengardeni". Plants were saline-irrigated with three watering regimes during tillering, heading, and grain filling stages. Biochemical traits, carbon isotope discrimination (Δ 13 C), mineral composition, grain yield (GY) and water use efficiency based on grain yield (WUE gy ) were evaluated as performance indicators. Almost all of the studied traits (e.g. soluble carbohydrates, proline, ∆ 13 C, Na concentration, and GY) were significantly affected by deficient saline-irrigation regimes at different growth stages. The hierarchical clustering analysis clearly showed that Δ 13 C placed very close to GY averaging two barley landraces, which was in accordance with the scatter plot result. Multiple linear regression performed between GY as the dependent variable and other traits studied as the independent variables indicated that WUE gy , Δ 13 C, and soluble carbohydrates significantly explained the variability in GY ( R 2 =95.64%). A significant positive correlation that observed between ∆ 13 C and GY at three growth stages, indicated that ∆ 13 C may be an important proxy component for indirect selection of yield potential in barley under deficient irrigation regimes with saline water. According to our result, "Karkeni" seems to be more efficient in terms of higher GY, WUE gy , proline and carbohydrate contents, K, Mg and Zn concentrations, as well as lower Δ 13 C and lipid peroxidation as compared with "Bengardeni", under low osmotic potential imposed by deficient irrigation treatments with saline water, "Karkeni" can thus be selected and used as a parent in order to obtain more tolerant plants against such stresses in future breeding programs., (© 2018 The Japanese Society for Plant Cell and Molecular Biology.)