Contact‐uptake of iron from vermiculite by maize

Abstract

By means of modified two‐phase experiments, uptake of FeIII from vermiculite by maize (Zea mays L., cv. Mutin) was investigated. The solution phase consisted of Hoagland I with and without Fe. In the presence of FeEDDHA in the growth medium, leaf concentration of Fe was 2.5‐fold and Mg 2.3‐fold greater, P 4.8‐fold and K 1.2‐fold smaller in plants with roots in contact with vermiculite than in plants with roots suspended in nutrient solution. In the absence of FeEDDHA in the growth medium, growth was twofold, leaf concentration of Fe 4.2‐fold, chlorophyll b 4.2‐fold, and chlorophyll a 9.0‐fold greater and K 1.4‐fold, Ca 2.7‐fold, and P 5.2‐fold smaller in plants with roots in contact with vermiculite than in plants with roots suspended in nutrient solution. The leaf concentrations of Fe and chlorophyll a and b in plants receiving no FeEDDHA but having their roots in contact with vermiculite were equal to those in plants with roots suspended in solution containing 100 μmol L^‐1 FeEDDHA. The data indicate that contact between roots and solid (Fe‐containing) substrates is a prerequisite for the mobilization of sparingly soluble Fe and can also increase the uptake of Fe from FeEDDHA. Availability of Felll present in vermiculite to maize shows that, aside from improving the physical properties of potting mixtures, vermiculite could also be a source of Fe for some plants.