Boron alleviates the aluminum toxicity in buckwheat by regulating antioxidant defense system and maintaining osmotic balance

Aluminum (Al) pollution in acidic soils has become a serious environmental problem worldwide. Boron can help plants mitigate aluminum phytotoxicity in acidic soils, but its underlying mechanism in buckwheat remains completely unknown. In this study, the buckwheat germination and greenhouse pot experiments were carried out under the conditions of four Al concentrations (0, 5, 10, and 15 mM) and four boron concentrations (0, 10, 30, and 50 µM). This research aimed to investigate the mitigation effect of exogenous boron on the Al toxicity of buckwheat and reveal the mechanism from the aspects of growth characteristics, antioxidant enzyme system, and osmotic regulation. The results showed that boron supply reduced the accumulation of Al in buckwheat roots, increased the antioxidant enzyme activity and the content of osmotic adjustment substances in roots and leaves, reduced the Al damage to root and leaf cells, maintained the osmotic balance of the cells, improved the root activity and the content of leaf photosynthetic pigment, ultimately leading to a significant increase in buckwheat biomass. In conclusion, different levels of boron treatment increased the tolerance of buckwheat root and leave to Al toxicity, and had a promoting effect on the growth of buckwheat. Therefore, applying boron is a promising green remediation technique to improve crop tolerance in Al-contaminated acidic soil.