The dieca effect in the respiration of barley

Results previously described for the respiration of barley root tips lead to the conclusion that their cytochrome system temporarily gives way to a copper-dependent system a few days after germination. Independent work with related species does not suggest similar effects. A simultaneous comparison of barley and wheat root tips has therefore been carried out and has given results in full agreement with previous work for both species. The change, referred to here as ‘the dieca effect’, occurs in barley and not in wheat. It indicates that a drastic alteration of oxidation mechanism may occur in a rapidly growing tissue without apparent disturbance to growth or salt uptake by the tissue.