Effects of copper deficiency on root nodules of subterranean clover

Effects of copper deficiency on the development of subterranean clover root nodules were studied. These included a depression of the bacteroid content, an accumulation of starch in the invaded cells and a reduction in the rate of development of the nodule apex. A similar pattern of increasing severity of metabolic effects in the youngest tissues was also found in leaves, but at a later stage of plant development than in nodules. At low copper supply the copper content of tissues and the activity of known copper-containing enzymes was depressed. The relevance of the observations to the disturbance of metabolism within the low copper nodules was discussed. It was suggested that low activity of copper containing enzymes (e.g. cytochrome c oxidase) might be important for maintenance of low oxygen tension within the nodule cells essential for nitrogen fixing activity.