Wheat genotypes differing in aluminum tolerance differ in their growth response to CO(2) enrichment in acid soils

Aluminum (Al) toxicity is a major factor limiting plant growth in acid soils. Elevated atmospheric CO(2) [CO(2)] enhances plant growth. However, there is no report on the effect of elevated [CO(2)] on growth of plant genotypes differing in Al tolerance grown in acid soils. We investigated the effect of short-term elevated [CO(2)] on growth of Al-tolerant (ET8) and Al-sensitive (ES8) wheat plants and malate exudation from root apices by growing them in acid soils under ambient [CO(2)] and elevated [CO(2)] using open-top chambers. Exposure of ET8 plants to elevated [CO(2)] enhanced root biomass only. In contrast, shoot biomass of ES8 was enhanced by elevated [CO(2)]. Given that exudation of malate to detoxify apoplastic Al is a mechanism for Al tolerance in wheat plants, ET8 plants exuded greater amounts of malate from root apices than ES8 plants under both ambient and elevated [CO(2)]. These results indicate that elevated [CO(2)] has no effect on malate exudation in both ET8 and ES8 plants. These novel findings have important implications for our understanding how plants respond to elevated [CO(2)] grown in unfavorable edaphic conditions in general and in acid soils in particular.