CHELATOR EDTA IN NUTRIENT SOLUTION DECREASES GROWTH OF WHEAT

ABSTRACT

Chelators have routinely been used to supply iron (Fe) in the nutrient solutions for growing plants. However, potential toxicity of these chelators to plants has not been assessed hitherto. In this study, wheat was grown in the presence or absence of EDTA (ethylenediaminetetraacetic acid) in the nutrient solution (with Fe supplied to plants as a foliar spray of Fe citrate). The effects of these treatments were compared with Fe(III)EDTA supplied to the nutrient solution. Plants grown in EDTA-containing nutrient solutions had lower biomass of roots, and especially shoots, in comparison to the plants grown in the EDTA-free solution. Greater accumulation of Fe in shoots occurred in the treatments with Fe foliar sprays compared to Fe supplied in the nutrient solution. In the treatments with foliarly-applied Fe, roots contained sufficient amounts of Fe, indicating good transport of Fe citrate in the phloem. Greater accumulation of zinc (Zn) and copper (Cu) occurred in roots and shoots of plants growing in the EDTA-free nutrient solution than in the EDTA-containing solutions. Such an effect was also observed for manganese (Mn), but to a smaller extent and only in 19-day-old shoots. In contrast, roots accumulated more Mn when grown in the Fe(III)EDTA solutions than in treatments where Fe was supplied to the foliage. The amount of Zn and Cu transported from roots to shoots was greater in plants grown in EDTA-free nutrient solution compared to EDTA-containing solutions, reflecting greater accumulation of these micronutrients by roots. In conclusion, EDTA in nutrient solutions can affect plant growth. Thus, for experimental work involving EDTA, it will be necessary to establish absence of interactions between EDTA-related growth reduction and the treatments under study.

ACKNOWLEDGMENTS

The author benefited greatly from discussions with late Professor H. Marschner, University of Hohenheim, Germany. Technical assistance with atomic absorption analyses by Mr. Ali Esna-Ashari is gratefully acknowledged. This work was supported through Research Fellowship to Z. R. from the Alexander von Humboldt Foundation. Further support was provided by the Australian Research Council and Deutsche Forschungsgemeinschaft.