Effect of Iron Supply on Growth, Chlorophyll, Tissue Iron and Activity of Certain Enzymes in Maize and Radish

Abstract

The optimal level of Fe supply for the maximal yield of Zea mays was 0.5 m[image]. and for radish Raphanus sativus 0.1 m[image]. Increase in Fe supply increased the Fe content of radish plants, but the Fe content of top parts of maize plants was poorly correlated with Fe supply. In both species, at the suboptimal levels of Fe supply where visual pathological effects of Fe deficiency appeared, not only chloro -phyll and the iron porphyrin enzymes catalase and peroxidase but also aldolase and phosphorylase, enzymes for which Fe is not known to be a cofactor in higher plants, were significantly depressed. Acid phos-phatase and ribonuclease in maize and radish and transaminase in radish were stimulated by Fe deficiency. The addition of Fe++ iron to the extracts of Fe-deficient plants did not increase the activity of aldolase or phosphorylase, nor did the Fe++ complexing agents, [alpha],[alpha]-dipridyl and o-phenanthroline, inhibit the activity of the 2 enzymes. But like catalase and peroxidase, aldolase and phosphorylase were largely restored to normal level within 72-96 hours after application of additional (1 m[image]) Fe to deficient plants. It appears that Fe determines the synthesis or the activity of some compound necessary for the formation of the specific proteins, aldolase and phosphorylase. The depression of some enzymes and stimulation of others in Fe-deficient plants would further suggest that Fe deficiency upsets the normal balance in the formation of specific proteins, the enzymes.