Effects of lanthanum and cerium on the growth and mineral nutrition of corn and mungbean.

OBJECTIVE

Plant growth responses to the rare earth elements lanthanum (La) and cerium (Ce) have been reported, but little is known about the effects of these two elements on plant mineral nutrition.

METHODS

Corn (Zea mays 'Hycorn 82') and mungbean (Vigna radiata 'Berken') were grown in continuous flowing nutrient solutions containing 0, 0.2, 1.0 and 5.0 microm La or Ce. At harvest plants were divided into roots and shoots, dried, weighed and analysed for macro- and micronutrients, as well as for La and Ce.

RESULTS

La and Ce did not increase the growth of corn or mungbean. The dry weight of corn shoots was decreased by 32 % in the presence of 5.0 microm Ce; the other La and Ce concentrations had no effect. La and Ce concentrations of 0.9 and 5.0 microm decreased the shoot dry weight of mungbean by 75 or 95 %, the two elements having closely similar effects. Decreases in the uptake of Ca, Na, Zn and Mn by corn were observed with increases in solution La and Ce. For mungbean, the uptake rates of all measured elements decreased with increases in solution La and Ce. The concentrations of La and Ce in the roots of both species were higher than in the shoots and increased strongly with increasing concentrations of La or Ce in solution. The La and Ce concentrations in mungbean shoots were always higher than in corn shoots.

CONCLUSIONS

La and Ce did not enhance the growth of corn or mungbean, but decreased the growth, root function and consequently the nutritional status of mungbean at concentrations >0.2 microm in solution. It is concluded that if La or Ce have positive effects on corn and mungbean growth, they can only occur at solution concentrations below 0.2 microm.