Wheat genotypes differing in aluminum tolerance differ in their growth response to CO2 enrichment in acid soils

Abstract

Aluminum (Al) toxicity is a major factor limiting plant growth in acid soils. Elevated atmospheric CO2 [CO2] enhances plant growth. However, there is no report on the effect of elevated [CO2] on growth of plant genotypes differing in Al tolerance grown in acid soils. We investigated the effect of short-term elevated [CO2] 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 [CO2] and elevated [CO2] using open-top chambers. Exposure of ET8 plants to elevated [CO2] enhanced root biomass only. In contrast, shoot biomass of ES8 was enhanced by elevated [CO2]. 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 [CO2]. These results indicate that elevated [CO2] 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 [CO2] grown in unfavorable edaphic conditions in general and in acid soils in particular. Wheat genotypes with contrasting tolerance to aluminium showed different growth response to elevated CO2 when grown in acid soil. Exudation of malate from root apices of aluminum-tolerant ET8 genotype was greater than those of Al-sensitive ES8 genotype under both ambient and elevated CO2, and the malate exudation rate expressed on individual root apex was not affected by elevated CO2. These results have important implications for our understanding how plants respond to elevated [CO2] grown in unfavorable edaphic conditions in general and in acid soils in particular. © 2013 The Authors. Ecology and Evolution.