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Uptake of Cadmium—Its Toxicity, and Effect on the Iron Ratio in Hydroponically Grown Corn¹

ABSTRACT

The uptake of cadmium by corn roots (Zea mays L.) and shoots from hydroponic solutions was determined over time intervals from 3–12 days. This uptake from solutions containing 1–40 mg cadmium/liter of solution was correlated with leaf chlorophyll content, dry matter production, and tissue concentration of zinc and iron. Cadmium concentration in roots and shoots increased with increased time of treatment. Roots of plants treated for 12 days contained about twice the cadmium found in shoots (approximately 200–1,100 µg cadmium/g dry weight in roots and approximately 100–450 µg cadmium/g dry weight in leaves). The dry weight of both roots and shoots, and of leaf chlorophyll concentration, decreased with increased cadmium tissue concentrations. The zinc concentration decreased, but the iron concentration increased, in leaves and roots as the cadmium concentration increased. These data resulted in a linear relationship between the increase of tissue cadmium and the increasing iron/zinc ratio. While the chlorosis of cadmium-treated leaves appeared to be comparable to that resulting from iron deficiency, the data presented indicate that an iron deficiency is not the cause of leaf chlorosis in cadmium-treated plants. A more important factor in cadmium toxicity may be the apparent correlation between an increase in tissue cadmium concentrations and the corresponding increase in the iron/zinc ratio.

Key Words: heavy metal pollution • chlorosis • ion uptake

¹ Contribution from the Department of Agronomy, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801. Supported in part by funds from the Illinois Agricultural Experiment Station and from NSF RANN grant GI-31605. We gratefully acknowledge the technical assistance of Mr. Richard Moore and the Environmental Research Laboratory, Univ. of Illinois, for sample analysis.

² Present address: Agricultural Experiment Station, College of Agriculture, Univ. of Idaho, Moscow, ID 83843.

³ Research Associate, Professor, and Associate Professor, Dep. of Agronomy, Univ. of Illinois at Urbana-Champaign.

Received for publication June 8, 1973.