Abstract
The rate of penetration of brucine (from a solution of brucine sulphate) into the vacuole of a living cell of Nitella is much greater with the external solution at pH 9.3 than at pH 5.5. At pH 9.3 brucine accumulates in the sap and becomes more concentrated than in the external solution. As brucine penetrates, the pH value of the sap in the vacuole in increased. (The brucine is tested with nitric acid and the pH value with indicators.)
When cells exposed to brucine sulphate solution are transferred to a buffer solution containing no brucine the rate of exit of brucine from the vacuole is greater when the buffer solution is at pH 5.5 than at pH 9.3. The difference in the rate caused by the variation in the external pH value is less marked with exit than with penetration.
As brucine comes out of the vacuole the pH value of the sap is decreased.
The same result is obtained with penetration of brucine into the “vacuole” of an artificial system consisting of a layer of chloroform placed between the brucine sulphate solution and the sap in a U-tube.
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