Determination of sugar components in each sap was
carried out by high performance liquid chromatography
(HPLC; Shimadzu LC-20A) with a CAROBO-Sep CHO-682
(7.8 mm I.D., 300 mm, TRANSGENOMIC) column at 80 C.
Distilled water was used for the solvent at a flow rate of
0.4 ml min1 with a refractive index detector. Ribose was used
as an internal standard and calibration curves were made for
individual sugars, using commercial products purchased from
Wako Pure Chemical Industries Ltd.