Interrelationship of Iron and Manganese Supply in Growth, Chlorophyll, and Iron Porphyrin Enzymes in Barley Plants.

Somers and Shive (37) suggested that the physiological availability of iron in plants is determined by the relative manganese supply and that the optimum growth and yield of plants depend on a certain definite proportion rather than the absolute level of iron and manganese supply. These workers also held that iron deficiency is identical with manganese excess and iron excess with manganese deficiency, the 2 elements having a mutually antagonistic effect. Twyman (40) and Weinstein and Robbins (42) observed a close similarity between the effect of iron deficiency and manganese excess but the experimental evidence obtained by Berger and Gerloff (8), Hewitt (15, 16), and Morris and Pierre (24) indicated that in many plants the effects of the 2 were quite distinct. To find out if a definite ratio of iron and manganese supply is necessary for optimal growth of barley, and to learn if the deficiency of iron is identical with manganese excess, we investigated the interaction of iron and manganese as it relates to the growth, visual pathological effects, chlorophyll, nutrient uptake, sugars, protein, and nonprotein nitrogen, and iron porphyrin enzymes in barley. This paper describes the interaction of iron and manganese as it relates to the growth, dry matter yield, chlorophyll content, and the iron porphyrin enzymes. In mature barley plants efforts to measure cytochrome oxidase were not successful and the study of iron porphyrin enzymes was confined to catalase and peroxidase.