Potassium effect on iron stress in tomato

Tomato plants, two Fe‐efficient cultivars and one Fe‐inefficient cultivar, were grown in treatment combinations of normal and low Fe and K concentrations (Normal Fe, Normal K; Low Fe, Normal K; Low Fe, Low K). Iron‐stressed plants with normal K levels were the first to show elevation of root proton excretion and an enhanced ability to regreen. Roots from the Fe‐efficient cultivars had a marked increase in the rate of CO₂ dark fixation that was most prominent with a Normal K, Low Fe. The amount of ¹⁴C labeling of root organic acids, particularly malate, citrate, lactate and oxaloacetate increased under Fe‐stress conditions in the Fe‐efficient cultivars; Fe stress with low K resulted in less ¹⁴C labeling. A scheme for Fe reduction, uptake and transport is discussed related to CO₂ fixation and organic acids (malate, citrate and oxaloacetate.)

¹Part of the research done by the senior author while on leave at the Institute for Whole Body Metabolism, Inba, Chiba, Japan. The helpful assistance of Mr. Y. Mabuchi and T. Sakemoto is recognized.