Detached Kalanchoě leaves were placed in the dark and changes in the amounts of total soluble N, asparagine, glutamine, amino N, ammonia, and titratable acid were followed during the periods of acidification and deacidification. Abundant starch was present throughout the experiments. The amount of acid which accumulated in the initial period was increased by placing the leaves in 5 per cent. CO 2 and also by decreasing the temperature from 25 to 10°. In neither case were the nitrogen fractions affected in a similar way to the acid levels. No consistent relationship could be found between the amount or change in amount of acid and the amounts of the nitrogen fractions. Over prolonged periods the drifts in the amounts of the nitrogen fractions were very similar to those known in non-succulent leaves. It is concluded that, despite the large amounts of free acid and starch present, the nitrogen metabolism of detached Kalanchoě leaves in the dark is similar to that of non-succulent leaves. A possible explanation is suggested for the incorporation of 14C from 14CO 2 into nitrogenous substances in Kalanchoě leaves during dark acidification. Changes in the amounts of glutamine, which seemed to be related to oxygen uptake rather than to acid fluctuations, were measured in comparable leaf samples showing different rates of oxygen uptake. The rate of oxygen uptake of leaves and leaf disks in the dark was controlled by placing them in an atmosphere of nitrogen, or 5, 20, or 100 per cent, oxygen, by the addition of 10–3 M. cyanide, or by varying the temperature. At the end of a given period the amount of glutamine was always greater in the samples which had shown the higher rate of oxygen uptake during this perod. This correlation was found irrespective of whether the amount of glutamine had increased or decreased. With the assumptions that glutamine production and consumption were proceeding simultaneously and that the rate of consumption was unaffected by the rate of oxygen uptake, the experimental values are consistent with the hypothesis that the rate of glutamine production and the rate of oxygen uptake were directly related. The possible significance of these findings is discussed.
Copyright (C) 1962, Society for Experimental Biology
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