Boron alleviates aluminum toxicity in pea (Pisum sativum)

Abstract

One important target of boron (B) deficiency and aluminum (Al) toxicity is cell wall. Thus we studied the hypothesis that B is capable of alleviating Al toxicity in pea (Pisum sativum). Short-term and prolonged Al exposure to pea roots at different B levels was carried out on uniform seedlings pre-cultured at a low B level. When seedlings with a low B level were supplied with or without B for 1 and 2 days before 24 h Al exposure, roots were longer while root diameter was thinner after B addition especially for 2 days even with exposure to Al; root elongation was inhibited while root diameter was enlarged by Al exposure. Callose induction by Al toxicity was higher with B added, but this was reversed after the removal of the cotyledons. Hematoxylin staining was lighter in the root tips given B, and Al content in the root tips and cell walls dropped after exposure to B. This indicates that B alleviated Al toxicity in the root tips during short-term Al exposure by decreasing Al binding in root cell walls. An increase in chlorophyll and biomass and reduced chlorosis were found at the higher level of B during prolonged Al treatment, which was coincided with the decreased Al contents, indicating that B alleviated Al toxicity to shoots. B supplementation alleviates some of the consequences of Al toxicity by limiting some Al binding in cell walls, resulting in less injury to the roots as well as less injury to the shoots.