Ascorbic acid (ASC) is a molecule naturally synthesized in plant cells, protecting against abiotic stresses by reducing reactive oxygen species (ROS), which cause oxidative damage. Aluminum (Al) toxicity is the major limiting factor on crop productivity in acidic soils, increasing ROS within cells and impairing the growth and development of plants. Exogenous antioxidant applications are an effective strategy to promote tolerance to abiotic stress. The objective was to evaluate the effect of foliar ASC applications (0, 50, 100, 200, and 400 mg L-1 ASC) and their interaction with Al toxicity (0, 400 mu M Al) in Star, an Al-sensitive cultivar of highbush blueberry. Significant increases of 1.6-fold in growth were observed in roots and leaves under treatment with 200 mg L-1 ASC. In the same treatment, increased pigments and antioxidant activity (similar to 1.2- to 2.3-fold) were observed concomitant with reduced lipid peroxidation. Positive correlations between organic acid exudation, the ASC/DHA ratio, and calcium levels were observed, whereas a negative correlation between lipid peroxidation and dehydroascorbate (DHA) was observed. Foliar ASC application also increased the ASC/DHA ratio in leaves and enhanced 2.2-fold organic acid exudation in the 200 mg L-1 ASC treatment. The results suggest that foliar ASC applications improved redox balance and underscore the potential of ASC as a practical solution to enhance resilience in Al-sensitive plants.

AimTo examine the effect of active aluminum (Al) on copper(II) (Cu(II)) bioavailability in an acidic Cu-contaminated soil and uptake of Cu(II) by Chinese cabbage.MethodsA pot trial was conducted with Ca(OH)2 and peanut straw biochar (PB) to investigate Cu(II) uptake by Chinese cabbage. DGT (CDGT-Cu) and CaCl2 extraction methods (CCaCl2-Cu) were used to determine soil available Cu(II) and BCR sequential-extraction was used to determine Cu(II) species in the soil.ResultsThe amelioration of soil acidity with Ca(OH)2 and PB increased soil pH, promoted Chinese cabbage growth, and decreased Cu(II) uptake by plant shoots/roots. There were highly significant positive linear correlations between CDGT-Cu, CCaCl2-Cu and Cu(II) uptake by plant shoots. CDGT-Cu showed a better predictive effect for Cu(II) uptake by plant roots with a greater correlation coefficient (R2 = 0.9756). Thus, the DGT method was more effective in predicting Cu(II) uptake by plants. With increasing soil pH, Cu-HOAc and Cu-Reducible were converted to Cu-Residual, resulting in a decrease in soil Cu(II) bioavailability. The results of Structural Equation Modeling analyses showed that Al uptake by Chinese cabbage had a promoting effect on Cu(II) uptake by the plant, mainly through affecting plant growth indirectly. Soil exchangeable Al inhibited root growth (root length, root dry weight), reduced root resistance of Chinese cabbage and indirectly increased Cu(II) uptake.ConclusionsReducing Al toxicity decreased root damage and Cu(II) uptake by plant, improving the edible quality of Chinese cabbage. When remediating acidic Cu-contaminated soils, more attentions should be payed to mitigating and regulating Al toxicity.

Aluminum (Al), prevalent in the crust of the Earth, jeopardizes plant health in acidic soils, hindering root growth and overall development. In this study, we first analysed the Al- and pH- tolerance of the Penicillium olsonii TLL1 strain (POT1; NRRL:68252) and investigated the potential for enhancing plant resilience under Al-rich acidic soil conditions. Our research illustrates the extraordinary tolerance of POT1 to both high Al concentrations and acidic conditions, showcasing its potential to alleviate Al-induced stress in plants. Metabolite analysis revealed that POT1 detoxifies Al through organic acid-dependent chelation mechanisms, significantly reducing Al stress in Arabidopsis and Pak Choi plants. Consequently, plant growth conditions improved, and the Al content in plant tissues decreased. Transcriptome analysis indicated that POT1 treatment downregulates genes associated with Al and oxidative stress such as MATE, ALS3, NIP1-2 and several peroxidases, highlighting its effectiveness in lessening Al-induced damage. Comparative assessments highlight the superior performance of POT1 compared to other Al-tolerant Penicillium species, attributed to its ability to thrive in diverse pH levels and effectively detoxify Al. These findings position POT1 as a promising agent for enhancing crop resilience in Al-compromised acidic soils, offering new avenues for promoting plant health and bolstering food security through increased crop yield and safety.

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.

Al toxicity is the main limiting factor for crop production in acidic soil, so this study is aimed to improve understanding of the effects of curcumin on the aluminum (Al) tolerance of grapes, Al-tolerant cultivation and the epigenetic mechanism of grapes exposed to Al. Vitis vinifera x V labrusca `Shuifing' cuttings were cultivated in greenhouse, which were exposed to 20 mmol L-1 aluminum sulfate and then treated with curcumin in different concentrations. Then, indicators of physiological resistance and the DNA methylation level of the grape leaves were measured. The results demonstrated that Al stress led to a series of physiological and biochemical changes in grape leaves and significantly increased DNA methylation levels. Specifically, the chlorophyll, protein, phosphorus (P) and potassium (K) content decreased, activity of superoxide dismutase (SOD) and peroxidase (POD) also decreased, while the proline, malonaldehyde and Al content increased drastically, resulting in damage to grape plants. However, treatment by 100 and 200 mu cool L-1 of curcumin led to significantly reduced DNA methylation levels and Al accumulation in grape leaves, reduced accumulation of malonaldehyde and proline, increased chlorophyll and protein content, enhanced SOD and POD activity, and improved intake of P and K. In summary, treatment by 100 and 200 mu mot Li curcumin had a significant effect on the Al tolerance of grapes, indicating that toxicity for grape cultivation in acidic soil.

The toxicity of aluminum (Al) in acidic soil inhibits plant root development and reduces crop yields. In the plant response to Al toxicity, the initiation of programmed cell death (PCD) appears to be an important mechanism for the elimination of Al-damaged cells to ensure plant survival. In a previous study, the type I metacaspase AhMC1 was found to regulate the Al stress response and to be essential for Al-induced PCD. However, the mechanism by which AhMC1 is altered in the peanut response to Al stress remained unclear. Here, we show that a nuclear protein, mutator-like transposable element 9A (AhMULE9A), directly interacts with AhMC1 in vitro and in vivo. This interaction occurs in the nucleus in peanut and is weakened during Al stress. Furthermore, a conserved C2HC zinc finger domain of AhMULE9A (residues 735-751) was shown to be required for its interaction with AhMC1. Overexpression of AhMULE9A in Arabidopsis and peanut strongly inhibited root growth with a loss of root cell viability under Al treatment. Conversely, knock down of AhMULE9A in peanut significantly reduced Al uptake and Al inhibition of root growth, and alleviated the occurrence of typical hallmarks of Al-induced PCD. These findings provide novel insight into the regulation of Al-induced PCD. Mutator-like transposable element 9A interacts with metacaspase 1 and plays an important regulatory role in the peanut response to Al stress.