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Millet is grass with high forage potential in semi-arid regions, both for its versatility of use and nutritional quality. The objective of this study was to evaluate the influence of a biostimulant and the plant extract (Cyperus rotundus) on the growth forage, and grain production in millet (cultivar IPA BULK 1BF) submitted to salt stress conditions. The research was carried out at the Serra Talhada Academic Unit, Federal Rural University of Pernambuco, in the Semiarid region of the Northeast of Brazil, from February to April 2017. The experiment was installed in randomized blocks, in a 3x4 factorial scheme, composed of a biostimulant (ACADIAN®), nutsedge extract, and the control, in four salinity levels of the irrigation water, electrical conductivities of 0, 1, 2 and 4 dS m-1, with four repetitions. Biometric analysis of all plants was carried out weekly to monitor crop growth. At 77 days after emergence, measures of net CO2 assimilation and transpiration rates were obtained. The harvest occurred with the maturation of the grains (ED9), being analyzed the dry mass of the different morphological components of the plant. The biostimulant at the level of 2 dS m-1 promoted an increase of 66% in the leaf area of millet compared to the control. With 4 dS m-1, the nutsedge extract provided an increase of 253% in the leaf area compared to the control. These expressive results obtained with the use of these compounds reflected in a production of dry leaf blade mass. The IPA BULK 1 BF millet cultivar has tolerance to the salinity levels studied in this research. The nutsedge extract and the biostimulant are alternatives capable of stimulating the growth and the production of forage of millet under the presence of salts in the irrigation water, however, these compounds have no influence on grain production

Saline‐alkali stress inhibited the normal growth and development of plants, which seriously restricted the yield of crops. Maize is one of the most important crops in the world. However, the mechanism of maize in response to saline‐alkali stress is still largely unknown. Through the observation of growth parameters and the detection of physiological and biochemical indicators in saline‐alkali tolerant (22KN3894) and saline‐alkali sensitive (H23146) maize inbred lines, this study found that compared with H23146, 22KN3894 accumulated less ROS content and more total flavonoids content, while the degree of root damage and ion toxicity was relatively small. Full‐length transcriptome and broadly targeted metabolome were used to analyse the response mechanism of extreme maize inbred lines to saline‐alkali stress. 22KN3894 accumulated more metabolites such as sugars and flavonoids. There were significant differences in the contents of flavonoid metabolites and genes related to flavonoid synthesis between the two materials. Weighted gene co‐expression network analysis and co‐expression network analysis based on RNA‐Seq data suggested that the ZmWRKY82 gene might respond to saline‐alkali stress by regulating the flavonoid biosynthesis pathway. ZmWRKY82 directly bound to the W‐box in the ZmCHI6 promoter and promoted its expression. The above results showed that ZmWRKY82 could improve the antioxidant capacity by promoting the transcription of ZmCHI6 and the synthesis of flavonoids, thereby resisting saline‐alkali stress. These findings provided novel insights for improving maize saline‐alkali stress tolerance, demonstrating that flavonoids played pivotal roles in plant stress adaptation, and laid the foundation for future mechanistic studies and breeding improvement.

Soil salinization, driven by rapid climate change, poses a serious threat to wheat (Triticum aestivum L.) production worldwide. The studies on the effect of sodium chloride stress on wheat have detailed reports, while the effects of Na2SO4, NaHCO3, and Na2CO3 stresses remain to be investigated. Here, we investigated the differential growth and physiological responses of wheat seedlings to equimolar concentrations of NaCl, Na2SO4, NaHCO3, and Na2CO3. Alkaline salts (NaHCO3 and Na2CO3) induced significantly more severe growth inhibition, chlorophyll degradation, and oxidative damage compared to neutral salts (NaCl and Na2SO4). This was evidenced by heightened lipid peroxidation, reactive oxygen species accumulation, and membrane injury, particularly under Na2CO3 stress. The antioxidant defenses were precisely tailored, which alkaline stress strongly activated ascorbate while neutral salts preferentially enhanced catalase activity. Osmotic adjustment was also stress‐specific, with alkaline conditions triggering extreme proline accumulation up to 7.5‐fold in roots. Ion homeostasis was profoundly disrupted under alkaline stress, marked by excessive Na+ uptake, severe K+ depletion, and significant reductions in nitrogen and phosphorus. Notably, gene expression analysis revealed stress‐specific regulation of key genes involved in ion transport (e.g., SOS1) and antioxidant defense. Our findings revealed distinct stress‐specific regulatory mechanisms in wheat, with alkaline causing more severe oxidative stress and membrane damage than salt. In addition, we examined the tissue expression and evolution of SOD genes, which showed the expansion and duplication of the SOD gene family in terrestrial plants. Our study unveils the divergent physiological pathways activated by different salts, providing novel insights into wheat stress adaptation and a theoretical basis for breeding salt‐tolerant cultivars. Chinese Spring (CS), Qing Mai 6 (QM), ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), Peroxidase(POD), Malondialdehyde, (MDA).

Saline‐alkali stress is one of the major abiotic stresses that severely affect rice yield. However, the mechanism by which saline‐alkali stress regulates grain filling in rice is still unclear. In this study, Oryza sativa L. spp. Indica cultivar Chaoyou1000 (C1000) was exposed to post‐anthesis saline‐alkali conditions at 6 days after anthesis, which significantly reduced the grain weight by suppressing the accumulation of starch and non‐structural carbohydrates in grains. Further analysis found that 1‐aminocyclopropane‐1‐carboxylate (ACC), a precursor for ethylene, was increased by saline‐alkali treatment. qRT‐PCR results showed that several key genes involved in ethylene biosynthesis, including the OsACS and OsACO genes, were upregulated in saline‐alkali‐treated grains. In addition, genes involved in the ethylene signalling pathway were also induced by saline‐alkali stress. Exogenous ethylene application reduced grain weight and both starch and NSC contents in grains of C1000, suggesting that saline‐alkali‐induced ethylene has a negative effect on grain filling. Furthermore, the gene expression levels of OsSUS, OsAGPL, OsAGPS, OsSSI and OsSSIIIa, which are key genes in the starch biosynthesis pathway, were downregulated in saline‐alkali‐treated grains. In agreement, assays on these enzymes further revealed that saline‐alkali stress decreased the activities of sucrose synthase (SUS), adenosine diphosphate glucose pyrophosphorylase (AGP) and starch synthase (StS). Together, our results indicated that saline‐alkali stress suppressed the enzyme activities involved in the conversion of sucrose to starch by elevating ethylene production, which led to inhibition of grain filling. Post‐anthesis saline‐alkali stress increases ethylene production by upregulating gene expression of ethylene biosynthesis, which thus activates ethylene signalling transduction in rice grains. Gene expression and enzyme activities for starch accumulation in rice grains are both decreased by elevated ethylene, resulting in decreased efficiency of starch biosynthesis and eventually lower grain weight.

Background Alhagi sparsifolia (Camelthorn)  is a leguminous shrub species that dominates the Taklimakan desert’s salty, hyperarid, and infertile landscapes in northwest China. Although this plant can colonize and spread in very saline soils, how it adapts to saline stress in the seedling stage remains unclear so a pot-based experiment was carried out to evaluate the effects of four different saline stress levels (0, 50, 150, and 300 mM) on the morphological and physio-biochemical responses in  A. sparsifolia  seedlings. Results Our results revealed that N-fixing  A. sparsifolia  has a variety of physio-biochemical anti-saline stress acclimations, including osmotic adjustments, enzymatic mechanisms, and the allocation of metabolic resources. Shoot–root growth and chlorophyll pigments significantly decreased under intermediate and high saline stress. Additionally, increasing levels of saline stress significantly increased Na + but decreased K + concentrations in roots and leaves, resulting in a decreased K + /Na + ratio and leaves accumulated more Na + and K + ions than roots, highlighting their ability to increase cellular osmolarity, favouring water fluxes from soil to leaves. Salt-induced higher lipid peroxidation significantly triggered antioxidant enzymes, both for mass-scavenging (catalase) and cytosolic fine-regulation (superoxide dismutase and peroxidase) of H 2 O 2 . Nitrate reductase and glutamine synthetase/glutamate synthase also increased at low and intermediate saline stress levels but decreased under higher stress levels. Soluble proteins and proline rose at all salt levels, whereas soluble sugars increased only at low and medium stress. The results show that when under low-to-intermediate saline stress, seedlings invest more energy in osmotic adjustments but shift their investment towards antioxidant defense mechanisms under high levels of saline stress. Conclusions Overall, our results suggest that  A. sparsifolia  seedlings tolerate low, intermediate, and high salt stress by promoting high antioxidant mechanisms, osmolytes accumulations, and the maintenance of mineral N assimilation. However, a gradual decline in growth with increasing salt levels could be attributed to the diversion of energy from growth to maintain salinity homeostasis and anti-stress oxidative mechanisms.

Saline-alkali stress is a widespread adversity that severely affects plant growth and productivity. Saline-alkaline soils are characterized by high salt content and high pH values, which simultaneously cause combined damage from osmotic stress, ionic toxicity, high pH and HCO3−/CO32− stress. In recent years, many determinants of salt tolerance have been identified and their regulatory mechanisms are fairly well understood. However, the mechanism by which plants respond to comprehensive saline-alkali stress remains largely unknown. This review summarizes recent advances in the physiological, biochemical and molecular mechanisms of plants tolerance to salinity or salt- alkali stress. Focused on the progress made in elucidating the regulation mechanisms adopted by plants in response to saline-alkali stress and present some new views on the understanding of plants in the face of comprehensive stress. Plants generally promote saline-alkali tolerance by maintaining pH and Na+ homeostasis, while the plants responding to HCO3−/CO32− stress are not exactly the same as high pH stress. We proposed that pH-tolerant or sensitive plants have evolved distinct mechanisms to adapt to saline-alkaline stress. Finally, we highlight the areas that require further research to reveal the new components of saline-alkali tolerance in plants and present the current and potential application of key determinants in breed improvement and molecular breeding.

Melatonin plays a crucial role in modulating metabolism and enhancing plant tolerance to biotic and abiotic stresses. This study investigated the mitigating effects of foliar-applied melatonin on growth and physiological responses of Daenian thyme ( Thymus daenensis ) under varying salinity stress in greenhouse conditions. A factorial experiment was conducted with four NaCl salinity levels (0, 40, 80, and 120 mM) and melatonin treatments (0 and 100 μM). Salinity significantly reduced plant biomass (fresh and dry shoot weight) and photosynthetic pigments (chlorophyll a, b, total chlorophyll, and carotenoids). Conversely, melatonin application improved these parameters across all salinity levels. Specifically, melatonin increased shoot dry weight by 16%, 18.5%, 3%, and 11.1% at 0, 40, 80, and 120 mM NaCl, respectively, compared to non-treated controls. Melatonin also substantially ameliorated chlorophyll content, with total chlorophyll increased by up to 42% under non-saline conditions. Furthermore, melatonin enhanced essential oil content at all salinity levels, achieving a maximum of 2.87% v/w at 40 mM NaCl. Photosystem II efficiency (F v /F m ) was highest in melatonin-treated plants under non-stress and lowest in untreated plants under severe salinity. Melatonin mitigated salinity-induced reductions in performance index (PI ABC ) and quantum yield of electron transport (ΦEo), while reducing energy dissipation parameters. Overall, foliar melatonin effectively alleviates salinity stress effects, promoting physiological resilience, growth, and essential oil production in Daenian thyme. These findings underscore the potential of melatonin as a practical strategy to enhance crop tolerance and productivity in saline environments.

Understanding the primary mechanisms for plant promotion under salt stress with plant growth promoting rhizobacteria (PGPR) inoculation of different salt-tolerant plant groups would be conducive to using PGPR efficiently. We conducted a meta-analysis to evaluate plant growth promotion and uncover its underlying mechanisms in salt-sensitive plants (SSP) and salt-tolerant plants (STP) with PGPR inoculation under salt stress. PGPR inoculation decreased proline, sodium ion (Na+) and malondialdehyde but increased plant biomass, nutrient acquisition (nitrogen, phosphorus, potassium ion (K+), calcium ion (Ca2+), and magnesium ion (Mg2+)), ion homeostasis (K+/Na+ ratio, Ca2+/Na+ ratio, and Mg2+/Na+ ratio), osmolytes accumulation (soluble sugar and soluble protein), antioxidants (superoxide dismutase), and photosynthesis (chlorophyll, carotenoid, and photosynthetic rate) in both SSP and STP. The effect size of total biomass positively correlated with the effect sizes of nutrient acquisition and the homeostasis of K+/Na+, and negatively correlated with the effect size of malondialdehyde in both SSP and STP. The effect size of total biomass also positively correlated with the effect sizes of carotenoid and the homeostasis in Ca2+/Na+ and Mg2+/Na+ and negatively correlated with the effect size of Na+ in SSP, but it only negatively correlated with the effect size of Ca2+ in STP. Our results suggest that the plant growth improvement depends on the nutrient acquisition enhancement in both SSP and STP, while ion homeostasis plays an important role and carotenoid may promote plant growth through protecting photosynthesis, reducing oxidative damage and promoting nutrient acquisition only in SSP after PGPR inoculation under salt stress.

Salinity is one of the most devastating environmental factors limiting crop productivity worldwide. Therefore, our study investigates the effect of seed priming with zinc oxide nanoparticles (ZnO NPs: 0, 50, and 100 mg L−1), 24-epibrassinolide (EBL: 0.0, 0.2, and 0.4 µM), and their combined treatments on maize (Zea mays L.) grown with different levels of saline stress (i.e., control, 5, 10 dS m−1) under semi-controlled conditions. Higher saline stress (10 dS m−1) negatively influenced the growth traits, physiological attributes, and elemental (i.e., Zn and K) uptake for both roots and shoots of maize, whereas it increased Na+ accumulation and Na+/K+ ratio in comparison to other treatments. However, seed priming with ZnO NPs and EBL as well as their combinations showed amelioration of the detrimental effects of saline stress on the growth and physiological and biochemical performance of maize. In general, seed priming with combined treatments of ZnO NPs and EBL were significantly more effective than either ZnO NPs or EBL as individual treatments. A combination of 100 mg L−1 ZnO NPS + 0.2 µM EBL resulted in the highest values of root length, root surface area, stem diameter, relative leaf water contents, total chlorophyll, net rate of photosynthesis, zinc accumulation, and K+ uptake, while it resulted in the lowest Na+ and Na+/K+ ratio, especially under the highest saline-stress treatment. Thus, we concluded that seed priming with combined ZnO NPs and EBL can effectively mitigate the saline-stress-mediated decline in the morphological, physiological, and biochemical traits of maize.

Background Drought and salinity are among the most critical abiotic stresses affecting crops worldwide. Within this context, melatonin has emerged as a multifunctional signaling molecule that mitigates stress and promotes growth in various plant species. This study aimed to evaluate the physiological and biochemical responses of Ocimum basilicum plants cultivated under hydroponic conditions and exposed to salt stress, following pre-harvest treatment with melatonin. Basil seedlings were immersed in melatonin solutions at concentrations ranging from 0 to 100 μM for 48 hours and subsequently grown for 60 days under saline stress. Results Melatonin treatment, particularly at 50 μM (T50), significantly increased the fresh weight of both aerial parts and roots. Aerial biomass nearly doubled, reaching 47.6 g plant⁻¹ compared to 23.8 g plant⁻¹ in untreated plants under salinity (+100%). Root fresh weight also rose markedly, from 29.6 g plant⁻¹ to 50.3 g plant⁻¹ (+69.8%). Leaf area expanded substantially, averaging 660.8 cm² per plant at T50 versus 301.2 cm² in salinity-stressed controls (+119.4%). Total chlorophyll content increased by 3.9–11.2%, with values rising from 43.43 µg cm⁻² in untreated plants under salinity to a maximum of 48.29 µg cm⁻² at 25 μM melatonin. Stomatal conductance showed a significant improvement as well, reaching 169.4 mmol m⁻² s⁻¹ at T50, which represented a 50.6% increase relative to untreated plants. Biochemical stress indicators declined consistently in melatonin-treated plants. MDA content decreased by 36.2% (from 3.87 to 2.47 nmol mg⁻¹ FW at T50), while foliar proline accumulation was reduced by 28.1% under the same treatment. Leaf total phenol content followed a similar trend, showing reductions ranging from 19.2 to 48.1% across all melatonin doses compared with salt-stressed controls. In most cases, these decreases were statistically significant (P<0.05), indicating improved redox homeostasis and membrane stability under salt stress. Conclusions Among the tested concentrations, 50 μM melatonin was the most effective in promoting growth and alleviating stress. These findings highlight its potential as a pre-harvest strategy to enhance basil performance under salinity within the broader context of melatonin-based stress management.