Articles
CARBOHYDRATES, ORGANIC ACIDS AND MINERAL ELEMENTS IN XYLEM SAP BLEEDING FROM KIWIFRUIT CANES
During the years 1986 and 1987 the sap bleeding from four canes per vine was collected for 24 hours at weekly intervals on five vines.
Each week the cut was renewed to stimulate bleeding.
Bleeding of the xylem sap occurred from 11 March 1986 to 30 April 1986 and from 1 April 1987 to 26 May 1987. The greatest amount of sap per vine collected during 24 hours was 89.0 ml in 1986 and 415.3 ml in 1987. The flow was low at the beginning of the bleeding, then increased reaching the maximum just before budburst.
The sap pH ranged from 5.31 to 5.86 in 1986, and from 5.53 to 6.61 in 1987. The maximum concentrations of glucose, fructose, sucrose, sorbitol and myo-inositol were respectively 307.7, 498.6, 156.9, 0.7 and 9.3 mg/1 in 1986, and 311.7, 480.1, 41.6, 3.5 and 1.0 mg/l in 1987. At the beginning of bleeding the sugar concentration was high; then it decreased around the budburst period.
Malic acid was detected at the maximum concentration of 708.6 and 470.4 mg/l in 1986 and 1987 respectively.
No tartaric acid was found.
In 1986 the sap had a lower concentration of the mineral elements than in 1987. The maximum concentrations in 1986 were respectively for total N, P, K, Ca and Mg 369.8, 92.5, 516.7, 729.2 and 133.3 mg/l.
In 1987 the maximum concentrations were respectively for total N, P, K, Ca and Mg 1942.0, 188.2, 2030,9, 1659.4 and 417.4 mg/l.
The variation of the concentration values during the period of bleeding followed a similar pattern in both years: low values at the beginning, followed by a maximum around the moment of budburst.
Plant and year variability seems to influence deeply the phenomenon.