Figure 6.

Proposed model for Al-induced citrate metabolism and secretion in the roots, and JA biosynthesis and signalling in the leaves of BX10 and BD2. In BX10, genes involved in citrate metabolism and exudation were induced in the roots. This finding suggested that more citrate could be secreted into rhizosphere for Al chelation, which is very essential for alleviating the Al toxicity in roots. Toxic Al³⁺ was continuously translocated through apoplastic and/or symplastic pathways. Genes involved in JA biosynthesis and signalling were highly induced in the leaves because much more Al³⁺ were accumulated in the leaves of sensitive soybean genotype. This finding indicated that JA-mediated defence response was activated, which could lead to resource and energy expenditure and growth arrest of leaves. These conditions are signs of Al toxicity.