Salinity is an important environmental stressor in arid, semi-arid, and coastal regions, primarily due to poor drainage, excessive fertilization, and proximity to the sea. Treating plants with exogenous organic acids may enhance their ability to survive under stressful conditions. In the present experiment, the effects of oxalic acid (OA) on strawberry plant growth and fruit quality were studied under salinity conditions. Day-neutral 'Albion' strawberry cultivar strawberry plants were planted in pots and 1 month after planting, salinity (35 mM Sodium chloride) and OA treatments (2.5, 5, 10 and 20 mM) were carried out. The plants were evaluated 60 days after the treatment's initiation. OA treatments decreased the electrical conductivity (EC) value of the soil under salinity. Salinity stress decreased root:shoot dry weight and the relative growth rate of plant biomass. OA treatments improved leaf cortical cell expansion and xylem conduit diameter under salinity conditions. L-ascorbic acid and malic acid increased with OA treatments. The study revealed that a 10-mM dose of OA was more effective than the other doses, indicating reduced salt stress damage. The results demonstrate that OA can be effectively used in strawberry cultivation under saline conditions.

Excessive heavy metal pollutants in soil seriously damage ecological systems and the environment. Dianthus spiculifolius shows strong tolerance to Cd/Pb and readily accumulates both metals. Isocitrate dehydrogenase (IDH) is key enzyme in the tricarboxylic acid cycle, which is involved in the plant response to a variety of abiotic stresses. Previous transcriptomic analyses suggested that DsIDH in D. spiculifolius plays a role in Cd/Pb detoxification. In this study, we found that the transcript level of DsIDH was significantly increased under Cd/Pb stress. Transiently expressed DsIDH localized at the chloroplasts in tobacco leaves. Transgenic yeast lines overexpressing DsIDH showed increased tolerance to Cd and Pb and decreased accumulation of Cd and Pb. Compared with their respective wild types, transgenic Arabidopsis and D. spiculifolius overexpressing DsIDH showed increased IDH activity, increased tolerance to Cd/Pb, and decreased heavy metal contents. The increased activity of IDH significantly accelerated the decomposition of isocitrate and increased the production of alpha-ketoglutaric acid and NADPH, which reduced damage caused by the reactive oxygen species produced in response to Cd and Pb stresses. The DsIDH might be a novel tolerance-related candidate gene useful for decreasing the storage of toxic heavy metals in crops.

The increasing level of cadmium (Cd) contamination in soil due to anthropogenic actions is a significant problem. This problem not only harms the natural environment, but it also causes major harm to human health via the food chain. The use of chelating agent is a useful strategy to avoid heavy metal uptake and accumulation in plants. In this study, randomized design pot experiment was conducted to evaluate potential role of malic acid (MA) and tartaric acid (TA) foliar spray to mitigate Cd stress in Spinacia oleracea L plants. For Cd stress, S. oleracea plants were treated with CdCl2 solution (100 mu M). For control, plants were given distilled water. One week after Cd stress, MA and TA foliar spray was employed at concentration of 100 and 150 mu M for both. The results of this study revealed that Cd stress (100 mu M) significantly reduced growth attributes, photosynthetic pigments and related parameters and gas exchange attributes. Cadmium stress also stimulated antioxidant defense mechanism in S. oleracea. Cd stressed plants had elevated levels of Cd metal ions in root and consumable parts (i.e. leaves) and caused severe oxidative damages in the form of increased lipid peroxidation and electrolytic leakage. MA and TA supplements at both low and high levels (100 and 150 mu M) effectively reversed the devastating effects of Cd stress and improved growth, photosynthesis and defense related attributes of S. oleracea plants. These supplements also prevented excessive accumulation of Cd metal ions as indicated by lowered Cd metal contents in MA and TA treated plants. These findings demonstrated that MA and TA treatments can potentially reduce Cdl induced phytotoxicity in plants by reducing its uptake and enhancing photosynthesis and defense related parameters.

In the unregulated co-landfill disposal of stabilized fly ash and municipal solid waste (MSW), the organic acid in MSW leachate poses a significant threat to the environmental safety of stabilized fly ash. Bulk bags (FIBCs)used for packaging stabilized fly ash may experience varying degrees of damage in landfill environments, which directly influence the percolation pathways of the invading liquid, subsequently affecting the leaching behavior of heavy metals in fly ash. A column leaching experiment was conducted to simulate the impact of organic acid on the leaching behavior and environmental risk associated with six heavy metals (Pb, Zn, Cu, Cd, Cr, Ni) in fly ash under multiple percolation paths. The findings suggest that the complex percolation paths can more effectively prevent heavy metals leaching from fly ash. Furthermore, the leaching of heavy metals is the lowest when the percolation path does not go through the bottom, with Pb, Zn, Cu, Cd, Cr and Ni being only 4.85 %, 27.36 %, 0.11 %, 2.22 %, 13.04 % and 0.42 % of the highest leaching amount under other paths (except Zn, the highest leaching of heavy metals is under the top in and bottom out path). Indicate that the integrity of FIBCs bottom significantly reduces the leaching of heavy metals, and favors environmental risk control of heavy metal, with the RI value did not reach the high-risk level (>= 600) in all stages. The percolation path has the most significant influence on the cumulative leaching amount of Cu, while it has the least influence on Zn. This influence is due to factors such as the contact degree of fly ash and organic acid, the transfer rate of heavy metals in liquid phase, and the properties of heavy metals. Heavy metal leaching was typically higher towards the end of the experiment, especially under the top in and bottom out path.

AimThe unregulated use of rare earth elements, such as Europium (Eu), may result in their build-up in soils. Here, we investigated how Eu affects wheat growth, photosynthesis, and redox homeostasis and how Arbuscular mycorrhizal fungi (AMF) may influence these processes.MethodsThe wheat plants were grown in soil with 1.09 mmol Eu3+/kg and/or AMF inoculation. The study is mainly based on a comprehensive examination of the detailed biochemical and metabolic mechanisms underlying the Eu stress mitigating impact of Eu by AMF in wheat plants.ResultsSoil contamination with Eu significantly induced a reduction in biomass accumulation and photosynthesis-related parameters, including photosynthetic rate (61%) and chlorophyll content (24.6%). On the other hand, AMF could counteract Eu's induced growth and photosynthesis inhibition. Under Eu stress, AMF colonization significantly increased fresh and dry weights by 43% and 23.5%, respectively, compared to Eu treatment. AMF colonization also induced minerals (e.g., Ca, K, Zn, and N) uptake under control and Eu stress conditions. By bolstering the antioxidant defense mechanisms, such as ROS-scavenging metabolites (flavonoids and polyphenols), AMF mitigated Eu-induced oxidative damage. In terms of the primary metabolites, organic acids, essential amino acids, and unsaturated fatty acids were increased by AMF colonization, particularly under Eu stress conditions.ConclusionApplying AMF is a workable approach for reducing Eu toxicity in wheat plants.

Cadmium (Cd), a widely distributed and highly toxic heavy metal, poses a severe threat to soil fertility and plant growth. Citric acid (CA), a small organic acid molecule, plays a crucial role in alleviating heavy metal toxicity in plants. However, the specific mechanism underlying how CA organizes and mitigates the damage caused by heavy metals to plant cells remains unclear. Therefore, we studied the impact of exogenous CA on Cd-induced stress in Iris tectorum. . The results showed that the addition of exogenous CA significantly increased the activity of antioxidant enzymes and altered the content of mineral elements including Fe, Zn, Ca, and Mn. Notably, compared to the Cd-only treatment, the proportion of Cd in the root cell walls increased by 14% in the presence of CA, and this increase was due to the ability of CA to regulate the amount of polysaccharide components in the root cell walls. CA affected the activity of pectinesterase (PME), changed the degree of pectinesterification (PMD), and enhanced the root cell walls' ability to bind Cd, thereby reducing the Cd content in the above-ground tissues and alleviating heavy metal toxicity in plants. In summary, this study provides robust evidence that supports the use of CA to improve the efficiency of urban soil remediation.

Main conclusion gamma-Aminobutyric acid alleviates acid-aluminum toxicity to roots associated with enhanced antioxidant metabolism as well as accumulation and transportation of citric and malic acids.AbstractAluminum (Al) toxicity has become the main limiting factor for crop growth and development in acidic soils and is further being aggravated worldwide due to continuous industrial pollution. The current study was designed to examine effects of GABA priming on alleviating acid-Al toxicity in terms of root growth, antioxidant defense, citrate and malate metabolisms, and extensive metabolites remodeling in roots under acidic conditions. Thirty-seven-day-old creeping bentgrass (Agrostis stolonifera) plants were used as test materials. Roots priming with or without 0.5 mM GABA for 3 days were cultivated in standard nutrient solution for 15 days as control or subjected to nutrient solution containing 5 mM AlCl36H2O for 15 days as acid-Al stress treatment. Roots were sampled for determinations of root characteristics, physiological and biochemical parameters, and metabolomics. GABA priming significantly alleviated acid-Al-induced root growth inhibition and oxidative damage, despite it promoted the accumulation of Al in roots. Analysis of metabolomics showed that GABA priming significantly increased accumulations of organic acids, amino acids, carbohydrates, and other metabolites in roots under acid-Al stress. In addition, GABA priming also significantly up-regulated key genes related to accumulation and transportation of malic and citric acids in roots under acid-Al stress. GABA-regulated metabolites participated in tricarboxylic acid cycle, GABA shunt, antioxidant defense system, and lipid metabolism, which played positive roles in reactive oxygen species scavenging, energy conversion, osmotic adjustment, and Al ion chelation in roots.

In acidic soils, aluminum (Al) toxicity inhibits the growth and development of plant roots and affects nutrient and water absorption, leading to reduced yield and quality. Therefore, it is crucial to investigate and identify candidate genes for Al tolerance and elucidate their physiological and molecular mechanisms under Al stress. In this study, we identified a new gene OsAlR3 regulating Al tolerance, and analyzed its mechanism from physiological, transcriptional and metabolic levels. Compared with the WT, malondialdehyde (MDA) and hydrogen peroxide (H2O2) content were significantly increased, superoxide dismutase (SOD) activity and citric acid (CA) content were significantly decreased in the osalr3 mutant lines when exposed to Al stress. Under Al stress, the osalr3 exhibited decreased expression of antioxidant-related genes and lower organic acid content compared with WT. Integrated transcriptome and metabolome analysis showed the phenylpropanoid biosynthetic pathway plays an important role in OsAlR3-mediated Al tolerance. Exogenous CA and oxalic acid (OA) could increase total root length and enhance the antioxidant capacity in the mutant lines under Al stress. Conclusively, we found a new gene OsAlR3 that positively regulates Al tolerance by promoting the chelation of Al ions through the secretion of organic acids, and increasing the expression of antioxidant genes.

Excessive aluminum (Al) in acidic soils is a primary factor that hinders plant growth. The objective of the present study was to investigate the effect and physiological mechanism of exogenous silicon (Si) in alleviating aluminum toxicity. Under hydroponic conditions, 4 mM Al significantly impeded the growth of white clover; however, pretreatments with 1 mM Si mitigated this inhibition, as evidenced by notable changes in growth indicators and physiological parameters. Exogenous silicon notably increased both shoot and root length of white clover and significantly decreased electrolyte leakage (EL) and malondialdehyde (MDA) content compared to aluminum treatments. This positive effect was particularly evident in the roots. Further analysis involving hematoxylin staining, scanning electron microscopy (SEM), and examination of organic acids (OAs) demonstrated that silicon relieved the accumulation of bioactive aluminum and ameliorated damage to root tissues in aluminum-stressed plants. Additionally, energy-dispersive X-ray (EDX) analysis revealed that additional silicon was primarily distributed in the root epidermal and cortical layers, effectively reducing the transport of aluminum and maintaining the balance of exchangeable cations absorption. These findings suggest that gradual silicon deposition in root tissues effectively prevents the absorption of biologically active aluminum, thereby reducing the risk of mineral nutrient deficiencies induced by aluminum stress, promoting organic acids exudation, and compartmentalizing aluminum in the outer layer of root tissues. This mechanism helps white clover alleviate the damage caused by aluminum toxicity.

Copper (Cu), with many documented cases of Cu toxicity in agriculture lands, is becoming an increasingly common issue in the world, but fewer studies have been conducted on its effects and alleviation strategies through the use of titanium dioxide nanoparticles (TiO2-NPs) and silicon (Si). For this purpose, we have conducted a pot experiment to determine the effects of seed priming with TiO2-NPs i.e., 40 mg L-1 and Si i.e., 3 mM on wheat (Triticum aestivum L.) under different levels of Cu in the soil i.e., 0 (no Cu), 100 and 200 mg kg(-1). Results from the present study showed that the increasing concentrations of Cu in the soil caused a significant decrease in the plant growth and biomass, chlorophyll pigments and gas-exchange characteristics, sugar content, essential ions in the roots and shoots of the plant, compared to control. In addition, increasing concentration of Cu also increases oxidative damage, enzymatic and non-enzymatic enzymes along with their gene expression, organic acids exudation patter and Cu concentration in the roots and shoots of the plant. The negative impact of Cu toxicity can overcome the application of TiO2-NPs and Si, which ultimately increased plant growth and biomass by capturing the reactive oxygen species (ROS), and decreased oxidative stress in T. aestivum by decreasing the Cu contents in the roots and shoots of the plants. Research findings, therefore, suggest that the combined application of TiO2-NPs and Si can ameliorate Cu toxicity in T. aestivum, resulting in improved plant growth and composition under metal stress, as depicted by balanced exudation of organic acids. [GRAPHICS]