100 g. As the concentration of free sugar in the sap increases from 83 to 153 mg ml1, the OPT sample gains 4.9 g of sugar in the sap in 30 days. At the same time, starch decreases from 3.5% to 0.5% of the solid, accounting for 0.9 g loss during this period. Starch is likely to be converted to glucose and fructose by the actions of enzymes including starch-degrading enzymes and sucrose metabolism enzymes. It has been reported that these enzymes are induced in plants by various kinds of stresses, such as cold stress [13], osmotic stress [14], and water stress [15], and consequently, monosaccharides and disaccharides accumulate. We presume the sugar accumulation in the sap of oil palm trunks occurs by induction of the enzymes triggered by the stress of felling.