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Application of growth regulators plays important role under salt conditions. Perspectives to overcome these limitations by chitosan nanoparticle (CSNP: 0, 0.25, 0.5, and 1%) and pyridoxine (PN: 0, 0.03, 0.06, and 0.09%) seed priming was studied in both experiments with milk thistle seeds exposed to NaCl as salt stress (0, 50, 100, and 150 mM). Salinity threshold and EC50 (the salinity level that 50% of germination reduction) achieved 74.85 and 213.5 mM, respectively. A significant reduction in germination percentage (49.12%), seedling length (50.07%), and seedling vigor index (67.39%) while, a significant increase in superoxide dismutase activity (54.63%) were achieved at 150 mM NaCl in compared to the control treatment. The highest germination rate was resulted by 100 mM NaCl and 0.25% CSNP and the least (2.86 seed/day) by 150 mM NaCl and without CSNP. The salt stress significantly decreased photosynthetic pigments; however, the largest value of chlorophyll a, b, and total was related to without NaCl and 1% CSNP and the least value of traits (6.1, 1.67, and 7.77 µg/g FW) to non-application of CSNP under 150 mM NaCl. PN application was caused decrease in free proline content compared to the non-application treatment. The most pronounced effects of CSNP and PN were recorded in 0.25 and 0.09% concentrations, respectively. The finding of this study leads to the conclusion that seed priming with CSNP and PN by improving physiological mechanisms such as photosynthetic pigment synthesis, antioxidant enzyme activities, and free proline content increased salt tolerance in milk thistle seedling.

Salinity is a major problem affecting crop production all over the world: 20% of cultivated land in the world, and 33% of irrigated land, are salt-affected and degraded. This process can be accentuated by climate change, excessive use of groundwater (mainly if close to the sea), increasing use of low-quality water in irrigation, and massive introduction of irrigation associated with intensive farming. Excessive soil salinity reduces the productivity of many agricultural crops, including most vegetables, which are particularly sensitive throughout the ontogeny of the plant. The salinity threshold (ECt) of the majority of vegetable crops is low (ranging from 1 to 2.5 dS m−1 in saturated soil extracts) and vegetable salt tolerance decreases when saline water is used for irrigation. The objective of this review is to discuss the effects of salinity on vegetable growth and how management practices (irrigation, drainage, and fertilization) can prevent soil and water salinization and mitigate the adverse effects of salinity.

The effects of sea level rise and coastal saltwater intrusion on wetland plants can extend well above the high-tide line due to drought, hurricanes, and groundwater intrusion. Research has examined how coastal salt marsh plant communities respond to increased flooding and salinity, but more inland coastal systems have received less attention. The aim of this study was to identify whether ground layer plants exhibit threshold responses to salinity exposure. We used two vegetation surveys throughout the Albemarle-Pamlico Peninsula (APP) of North Carolina, USA to assess vegetation in a low elevation landscape (≤ 3.8 m) experiencing high rates of sea level rise (3–4 mm/year). We examined the primary drivers of community composition change using Non-metric Multidimensional Scaling (NMDS) and used Threshold Indicator Taxa Analysis (TITAN) to detect thresholds of compositional change based on indicator taxa, in response to potential indicators of exposure to saltwater (Na, and the Σ Ca + Mg) and elevation. Salinity and elevation explained 64% of the variation in community composition, and we found two salinity thresholds for both soil Na⁺ (265 and 3843 g Na⁺/g) and Ca⁺ + Mg⁺ (42 and 126 μeq/g) where major changes in community composition occur on the APP. Similar sets of species showed sensitivity to these different metrics of salt exposure. Overall, our results showed that ground layer plants can be used as reliable indicators of salinity thresholds in coastal wetlands. These results can be used for monitoring salt exposure of ecosystems and for identifying areas at risk for undergoing future community shifts.

The perennial halophytic shrubs Atriplex nummularia and Rhagodia preissii are native to Australia and can be planted on saline land to produce sheep and cattle feed during the autumn. However, an impediment to the adoption of the species on saline land has been the challenges in achieving successful establishment by direct seeding due to a lack of knowledge of the optimal conditions for germination. Therefore, the optimal germination requirements in relation to temperature, salinity level and seed size was assessed for each species to ascertain the optimal conditions for successful establishment by direct seeding on saline land. Seeds of both species showed optimal germination temperature at 10°C. Atriplex nummularia seeds were more tolerant to temperatures above or below 10°C than R. preissii . The germination percentage of A. nummularia was unchanged at 0–200 mM NaCl 2 . The germination percentage of Rhagodia preissii declined when the NaCl 2 content exceeded 50 mM. There was no correlation between seed size, germination and emergence for any of the species. Based on the study, we suggest that sowing operations are performed during the cold winter months in subtropical areas or autumn and spring in temperate areas, to improve the successful establishment of these shrubs by direct seeding.

NERICA rice was developed through the hybridization of Oryza Glaberrima and Oryza sativa in an attempt to produce a higher yield in areas with a limited water supply. This study investigated the interactive effects of irrigation water salinities (0.38, 1.5, 3.0, 5.0, 7.0, 10.0 and 15 dSm−1) for various water depths (5, 10 and 15 cm) on crop yield and related components of NERICA rice variety. This study showed that increased levels of irrigation water salinity resulted in reduced rice yield, biomass weight, plant height, harvest index, 1000 grain weight, evapotranspiration, water use efficiency, stomatal conductance, and chlorophyll content, and increased plant sterility for all irrigation water depths. The threshold values of soil salinity for the NERICA rice for the 5, 10, and 15 cm depths were 2.14, 81 2.80, and 1.98 dSm−1, respectively. The study showed that the optimum salinity/water depth condition for the production of transplanted NERICA rice is irrigation water salinity < 1.50 dSm−1, and a 10 cm water depth. This irrigation water salinity level maintains the soil ECe at or below the salinity threshold value of 2.80 dSm−1. This study showed that NERICA rice has a salinity threshold value of 2.80 dSm−1. Since rice is generally considered to be more salt-sensitive during germination, it is recommended that farmers apply the least saline water available during the rice germination stage of growth. Information from this study will assist policymakers and farmers to better manage NERICA production in Sub-Saharan Africa.

Tall wheatgrass (Elytrigia elongata) has the potential to be utilized on marginal land, such as coastal saline-alkaline soils, to meet rising ruminant feed demand. However, the salinity threshold for cultivation of tall wheatgrass remains unclear, which restricts its extensive application. Here, a tall wheatgrass line, Zhongyan 1, was grown in saline-alkaline soils in the Yellow River Delta region to determine its salinity threshold. The results showed that the soil salinity of AM = 1.23, measured with a PNT3000 activity meter, led to only 5% dead plants of tall wheatgrass. Four grades of seedling plants were classified according to the morphological response of Zhongyan 1 to saline soils. The soil salinity declined while the survival rate and forage yield increased from grade 1 to grade 4 plants. Plant height and dry matter yield were negatively related to soil salinity. When the salinity in the soil depth of 0–10 cm was over 1%, the survival rate of tall wheatgrass declined dramatically with the increase in soil salinity. Under saline-alkaline stress, the plant height during 12–31 May was positively related to forage yield, which can be used as an indicator of productivity. The tall type (70–120 cm) produced 5627.2 kg ha−1 of dry matter, which was 3.32 times that of the dwarf type (20–69 cm). The forage yield of tall wheatgrass in saline-alkaline land was largely affected by the proportion of highly saline soil. Collectively, the soil salinity of 1% at a depth of 0–10 cm and the AM values of 1.23 measured with a PNT3000 activity meter can be used as the salinity threshold for cultivation of tall wheatgrass in coastal saline-alkaline land.

Plant tolerance to salinity stress is vital for irrigation scheduling, decision-making, planning and operation, and water resource management. This study is aimed to investigate the effects of irrigation water salinity on water use, growth, physiology, and yield parameters of drip-irrigated tomatoes in two different growing seasons. In addition to control (0.7 dS m−1), three irrigation water salinity levels: 2.5 (low), 5.0 (moderate), and 7.5 (high) dS m−1 were used. In both seasons, autumn 2021 and spring 2022, increased water salinities caused an increase in soil salinity, while a decrease in seasonal crop evapotranspiration. Plant heights did not show significant differences under different salinity levels in autumn 2021, while a meaningful difference among treatments was found in spring 2022. Marketable and total tomato yields, and the leaf area index showed significant decreases under increased salinities in both seasons. Stomatal conductance was not affected by salinity levels. The salt tolerance models for marketable and total fruit yields showed a low threshold and slope value in autumn 2021, contrasting with a high threshold and slope value determined in spring 2022. The results suggest that the salinity slope value should be considered, as well as the salinity threshold value, for decision making in tomato production at different growing seasons.

Enhancing the productivity and bioactivity of high-functional foods holds great significance. Carbon nanoparticles (CNPs) have a recognized capacity for boosting both plant growth and the efficacy of primary and secondary metabolites. Furthermore, while salinity diminishes plant growth, it concurrently amplifies the production of phytomolecules. To ensure the robust and sustainable production of nutritious food, it becomes essential to elevate biomolecule yield without compromising plant growth. Here, we assessed the CNPs priming on plant performance and metabolites of the glycophyte amaranth (Amaranthus hypochondriacus) sprouts at the threshold salinity (25 mM NaCl; i.e., salinity that does not reduce growth but enhances the metabolites of that plant). We measured growth parameters, pigment levels, and primary (carbohydrates, amino acids, organic acids, fatty acids) and secondary metabolites (phenolics, flavonoids, tocopherols). CNP priming significantly improved biomass accumulation (fresh and dry weight) and primary and secondary metabolites of amaranth sprouts. Increased photosynthetic pigments can explain these increases in photosynthesis. Enhanced photosynthesis induced carbohydrate production, providing a C source for producing bioactive primary and secondary metabolites. The priming effect of CNPs further enhanced the accumulation of essential amino acids, organic acids, unsaturated fatty acids, tocopherols, and phenolics at threshold salinity. The increase in bioactive metabolites under threshold salinity can explain the CNP priming impact on boosting the antioxidant activities (FRAP, DPPH, anti-lipid peroxidation, superoxide-anion-scavenger, hydroxyl-radical-scavenger, Fe-chelating and chain-breaking activity in aqueous and lipid phases) and antimicrobial activities against Gram-positive and Gram-negative bacteria and fungi. Overall, this study suggested that threshold salinity and CNP priming could be useful for enhancing amaranth sprouts’ growth and nutritional quality.

Screening salinity-tolerant plants is usually time intensive and only applicable to a limited number of salinity levels. A near-continuous gradient dosing (NCGD) system allows researchers to evaluate a large number of plants for salinity tolerance with multiple treatments, more flexibility, and reduced efforts of irrigation. Rose of sharon ( Hibiscus syriacus ), ninebark ( Physocarpus opulifolius ), and japanese spirea ( Spiraea japonica ) were irrigated using an NCGD system with eight electrical conductivity (EC) levels ranging from 0.9 to 6.5 dS·m –1 . At 11 weeks after irrigation was initiated, there were no significant differences among EC levels in terms of visual score, growth index [(Height + Width 1 + Width 2)/3], stem diameter, number of inflorescences, and shoot dry weight (DW) of rose of sharon. However, the root DW, relative chlorophyll content (SPAD), and net photosynthesis rate (P n ) of rose of sharon decreased linearly as EC levels increased. Ninebark and japanese spirea had increased foliar salt damage with increasing EC levels. The growth index, stem diameter, number of inflorescences, shoot and root DW, SPAD, and P n of ninebark decreased linearly as EC levels increased. The growth index and SPAD of japanese spirea decreased quadratically with increasing EC levels, but its stem diameter, number of inflorescences, shoot and root DW, and P n decreased linearly with increasing EC levels. The salinity threshold (50% loss of shoot DW) was 5.4 and 4.6 dS·m –1 , respectively, for ninebark and japanese spirea. We were not able to define the salinity threshold for rose of sharon in this study. However, rose of sharon was the most salinity-tolerant species among the three landscape plants.

【Objective】 The purpose of the study is to determine the appropriate irrigation water salinity threshold for winter wheat. Correlation analysis was conducted to find out the important growth, physiological and biochemical indexes related to wheat yield under different saline water irrigation. 【Method】 The pots experiment was conducted in 2019/20 season with two winter wheat varieties of SM22 and XY60 and four irrigation water salinities of 1 g/L, 3 g/L, 5g/L and 7 g/L. Irrigation water salinity with 1 g/L was taken as the control (CK). During the experiment, we measured the changes in yield, of wheat, as well as its physiological and biochemical traits in each treatment. 【Result】 The yield of both wheat varieties decreased as irrigation water salinity increased though at different rates. Compared with the CK, irrigating with saline water at concentration of 3, 5 and 7 g/L reduced the yield of SM22 by 3.23%, 24.19% and 51.61% respectively, and the yield of XY60 by 9.88%, 35.80% and 51.85% respectively. In terms of plant traits, increasing irrigation water salinity reduced the spike number and 1 000-kernel weight, plant height, flag leaf area, above- and below-ground biomasses, stomatal conductance, transpiration rate, net photosynthesis rate, chlorophyll content (SPAD) of the flag leaf, K+/Na+, Ca2+/Na+ and Mg2+/Na+ ratios in the leaves during grain-filling stage. All these reductions were at significant level. In contrast, it increased the proline content and Na+ content in leaves during the grain-filling period at significant level. In all treatments, the wheat yields were to be positively correlated to the following traits at significant level (p<0.05): 1 000-kernel weight with r=0.991, plant height with r=0.955, aboveground biomass with r=0.961, root biomass with r=0.835, SPAD with r=0.943, leaf K+/Na+ with r=0.908; and negatively correlated with the following traits at significant level (p<0.05): leaf proline content with r=-0.838, and Na+ content with r=-0.861. 【Conclusion】 The response of yield, growth, physiological and biochemical traits for the two wheat varieties to different irrigation water salinity had the similar trend. When irrigation water salinity was 7 g/L, there was significantly difference for the grain yield compared to the CK. Irrigation water salinity threshold of winter wheat was 3~5 g/L. In terms of traits which affect the ultimate yield, the1 000-kernel weight was the most important yield trait; plant height, above- and below-ground biomasses were the most important growth traits; flag leaf SPAD was the most important physiological trait; leaf proline content, Na+ content and K+/Na+ were the most important biochemical traits.