Effect of the arbuscular mycorrhizal symbiosis upon uptake of cesium and other cations by plants

Pot experiments were set up to determine the species-specific uptake of ces ium (Cs) by mycorrhizal (AM) and non-mycorrhizal (non-AM) plants. Using sta ble Cs and K application, side-effects of mineral fertilization (K) on AM d evelopment and uptake of Cs and the other cations Na, Ca and Mg were invest igated. AM colonization by the fungus Glomus mosseae led to a significant d ecrease in shoot Cs content of Agrostis tenuis from the first (4 weeks) to the third harvest (8 weeks). With regard to the root system, statistically significant differences were observed from the first (4 weeks) to the secon d harvest (6 weeks). Supply of additional K produced a significant decrease in Cs uptake by both AM and non-AM plants over a 10-week period. In the ca se of AM plant shoots, K fertilization did not very effectively reduce Cs u ptake by A. tenuis. Cs contents of fertilized AM roots were similar to non- AM controls. Potassium application resulted in an increase in K content and a slight reduction in Na and Mg contents of shoots and roots. Without K fe rtilization, the Na content of non-AM controls was significantly enhanced o ver AM shoots. Shoot and root Ca contents were generally higher without tha n with K addition. Negative side-effects of K fertilization as a countermea sure to Cs uptake were not observed in relation to AM development. The inte nsity of colonization by G. mosseae was not significantly depressed by K tr eatment. AM development in plants appeared to decrease Cs uptake, at least at moderate nutrient levels. It is possible that Cs is sequestered by AM ex traradical fungal hyphae and consequently not transferred to the plant to t he extent found in non-AM roots.