Xylem Sap from Actinidia chinensis: Apparent Differences in Sap Composition Arising from the Method of Collection

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Abstract
Large differences in composition were found between xylem sap collected from Actinidia chinensis (Chinese gooseberry or kiwi fruit) as bleeding sap and sap collected by vacuum extraction. A comparison of saps collected by the two methods has little meaning, however, unless the position on the plant from which sap was collected and the prior treatment of the plant are specified. Furthermore the composition of bleeding sap changes rapidly with time, probably because of marked gradients in concentration of individual solutes in the xylem sap from the base to the top of the plant. Contamination of vacuum-extracted sap by cellular contents was shown to be insignificant. Sap collected as bleeding sap and by vacuum extraction are of somewhat different origins. It would be difficult to predict the composition of bleeding sap simply from a knowledge of vacuum-extracted sap: it may be similarly unwise to predict the composition of the transpiration stream from that of vacuum extracted sap.