Relation of Manganese and Some other Metals to the Iron Status of Plants

Abstract

IT has been shown with piants growing in water culture that iron deficiency symptoms may be readiiy induced by excessive concentrations of manganous saits^1-6. A reciprocai effect on the incidence of manganese deficiency in the presence of high concentrations of iron compounds has aiso been shown for soya bean⁶ and some fruit crops⁴. These resuits have been interpreted⁶ as suggesting that iron deficiency and manganese toxicity are but reiative terms for the same disorder resuiting from too wide Fe/Mn ratios, and that manganese deficiency and iron toxicity are simiiariy reiative. It is generaiiy assumed that metaboiicaiiy active iron exists in piants in the ferrous state, and becomes inactive after oxidation to the ferric state. In one of the experiments referred to⁶, this oxidation was assumed to foiiow reaction with manganese compounds previousiy oxidized to a higher vaiency state. A simiiar abiiity to induce iron deficiency was forecast for cobait on account of its still higher oxidation-reduction potentiai than the manganese system postuiated, and some indication was obtained that iron deficiency was induced more readiiy by cobait saits.