Beneficial Effect of Rare Earth Elements on the Growth of Dryopteris Erythrosora

Lanthanum was demonstrated to be beneficial to the growth of Dryopteris erythrosora, a fern species which accumulates rare earth elements (REEs) under natural conditions. The enhancement of its growth by La was much greater than that by Ca. The uptake rates of REEs were evaluated to be higher than that of Zn and almost equal to those of Sr and Co. The region in the mesophyll where REEs were concentrated was not the same as that of Ca. In mesophyll cells, REEs were observed mainly in chloroplasts. These observations suggest that REEs do not behave as a ‹super Ca› as was suggested for some plants, but that they are transferred to chloroplasts by special mechanisms, possibly for fulfilling yet unknown functions or being stored as a mechanism of detoxification.