Research progress on alleviating aluminum stress of soybean in acidic soil

Soybeans have a unique nutritional profile containing oils, proteins, carbohydrates, and other beneficial nutrients. It is a major source of vegetable protein and oils and has the potential to be developed as a cash crop widely grown in all regions of the country. Soil acidification has become a soil pollution problem worldwide. Acidic soils in China cover about one-fifth of the country's arable land, threat agricultural production. Aluminium is the most abundant metal element in the soil and its toxicity is an important stressor that inhibits plant growth in acidic soil environments. Aluminium exists in the form of oxides and hydroxides when the pH is neutral and s not toxic to plants. When soil pH < 6.5, insoluble aluminium becomes exchangeable aluminium (mainly Al3+, Al(OH)(2+), Al(OH)(2)(+)). These forms of aluminium can inhibit plant root tip elongation by blocking nutrient exchange, interfere with plant water uptake, accumulate reactive oxygen species leading to lipid peroxidation in the plasma membrane, and cause cellular DNA damage leading to plant growth inhibition. In recent years, with the rapid development of industry and the emission of polluting gases leading to frequent acid rain, the acidity of our soils has been increasing and plants have been affected by aluminium stress to a progressively greater extent. Soil acidification and aluminium toxic stress have been one of the major factors limiting soybean production, with aluminium stress severely affecting the growth and development of soybean above and below ground. The soybean's root system is sensitive to aluminium toxicity. The level of aluminium aw round the root system can be a significant limitation to the soybean's growth, yield, and quality. Therefore, to understand the aluminium tolerance and manage the aluminium toxicity of soybeans, it is important to study the effects of aluminium ions on the soybean's growth, and its defence mechanisms against aluminium stress. This paper focuses on the toxic effects of aluminium toxicity on soybeans, describing the physiological, biochemical and genetic resistance mechanisms that occur in soybeans when exposed to aluminium stress and the changes in the biotic and abiotic environment of soybean roots under acidic soils. Based on this, the main physical, chemical and biological measures that may mitigate aluminium toxicity are biochar adsorption of aluminium ions, application of exogenous organic acids and mycorrhizal incorporation techniques. However, there are limitations to these traditional approaches, so we propose that further research is needed to investigate the molecular regulatory mechanisms of aluminium stress from a molecular biology perspective, such as compartmentalising the cytoplasm and vesicles and regulating the expression of aluminium toxicity tolerance genes in soybeans. In summary, this paper provides a reference for advancing research on aluminium tolerance in soybeans, enhancing the benefits of soybean cultivation, and for more in-depth research in the field of soil acidification and aluminium toxicity management in the hope of greater economic and ecological benefits.