Effect of cyanazine herbicide on VA mycorrhizal infection and growth ofPisum sativum

The effect of the photosynthetic inhibitor herbicide Cyanazine on VA mycorrhiza and on pea plant growth was examined. Plant growth was decreased by Cyanazine applied at the rate of 0.05 and 0.1 mg ml⁻¹. Cyanazine only decreased VA mycorrhiza of pea roots when applied at high doses (0.1 mg ml⁻¹). However, no direct effect of the herbicide on VA endophyte development was found. These results suggest that the inhibitory effect of Cyanazine on VA mycorrhiza took place via influence on plant metabolism and growth. VA mycorrhizas alleviated the deleterious effect of the herbicide on plant growth when applied at moderate (0.05 mg ml⁻¹) but not at high (0.1 mg ml⁻¹) doses.