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Dimethyl sulfoxide prevented loss of respiratory control and decrease in efficiency of oxidative phosphorylation when plant mitochondria were stored in liquid nitrogen. Respiration was severely inhibited and was not stimulated by adenosine diphosphate when mitochondria were frozen in liquid nitrogen without dimethyl sulfoxide. Thus, isolated mitochondria provide a model system for the study of the effects of freezing on biological membranes and of the prevention, by dimethyl sulfoxide, of freezing damage.

Germinating pollen of Lilium longiflorum (cv. Ace) briefly exhibited a high rate of respiration before pollen tubes began to grow. A second period of high respiration occurred while tubes were growing. Between these periods respiration proceeded at a lower rate. Respiration was stimulated by 2,4-dinitrophenol to occur at approximately the same rate in all three periods.