Oxidation of Ferrous Iron by Rice (Oryza sativaL.) Roots: a Mechanism for Waterlogging Tolerance?

Abstract

During an investigation of the resistance of rice (Oryza saliva L.) to ferrous iron toxicity in waterlogged soil, rice plants were grown in an oxygen-free agar medium containing known amounts of ferrous iron. Roots grown in this way deposited ferric iron on their surface in the same manner as those grown in waterlogged soil. Specimen roots were studied anatomically with the light microscope, and with the transmission electron microscope. Analyses of deposits within the roots were carried out using the electron microscope and electron probe analysis. Their distribution is described and it is suggested that gaseous oxygen, diffusing through cortical air spaces from the aerial part of the plant, is responsible for oxidation and precipitation of iron before it reaches the plant's conducting tissues, thereby preventing the uptake of toxic quantities.