The role of sorbitol in the C-metabolism of the Kelsey plum

Abstract

IT was shown in a previous communication [Donen, 1939] that, in the Kelsey plum sugars, acid and sorbitol were the most likely sources of C in the respiration of the detached fruit, and that their combined loss accounted satisfactorily for the depletion of dry weight during storage. In this paper an attempt is made to construct a balance sheet relating C lost by stored plums as C02 with the C lost as sugar, acid and sorbitol. Such a balance sheet is of some interest, as little information is available of the extent to which compounds other than sugars, or known precursors of sugars, contribute towards the C lost as C02 by respiring plant tissue. In the leaves of barley [Yemm, 1935], rhubarb [Vickery & Pucher, 1939], and wheat [Krotkov, 1939] as well as in germinating rice seedlings [Dastur & Desai, 1935] the loss of carbohydrates alone is insufficient to account for the output of C02. Proteins or some undetermined carbohydrates have been suggested as the possible sources of the excess C02. In the apple the loss of acid and sugar was found to be 17-30% greater than the C given off as C02 [Archbold & Barter, 1934]. Although the metabolisms of the apple and the leaf are possibly not directly comparable, nevertheless this result is the direct opposite of what has been found for detached leaves. In the plum the C lost as C02 can be, under certain conditions, almost completely accounted for in terms of loses of sorbitol, acid and sugar, but it will be shown that this conclusion may be greatly modified by the length and storage conditions of the experiment.