THE INFLUENCE OF soil AERATION ON THE EFFICIENCY OF VESICULAR–ARBUSCULAR MYCORRHIZAS

Abstract

Low concentrations of soil CO 2 increased but higher concentrations of CO 2 decreased the dry matter of mycorrhizal and non‐mycorrhizal plants of Eupatorium odoratum L. Dry matter of Guizotia abyssinica (L.f.) Cass. decreased linearly with increasing CO 2 . Shoot dry weight of Sorghum tricolor (L.) Moench was unaffected by increasing soil CO 2 . Inoculation with Glomus macrocarpum increased the dry matter of E. odoratum and Guizotia abyssinica significantly at all CO 2 concentrations. Mycorrhizal plants were more sensitive to soil CO 2 than were the non‐mycorrhizal plants. Carbon dioxide at concentrations up to 8% had little effect on mineral uptake (except N) by E. odoratum but 16% CO 2 decreased the mineral uptake significantly. Mineral uptake by Guizotia abyssinica decreased but the mineral concentration in the plant increased with rising CO 2 . The mineral uptake and concentration in 5. bicolor showed variable response to soil CO 2 . The efficiency of the mycorrhizal fungus Glomus macrocarpum in enhancing growth of its hosts was more affected by soil CO 2 than was its development in roots.