3/24/08

Monday, 8:30 AM. 10 degrees, wind S, very light to calm. Barometer predicts precipitation. Skies blue with some haze on the E horizon.
Clear and cold last night. If it warm up as predicted we should have some sap to haul by late afternoon. Sap flow in maples is not related to the normal transportation of water in trunk and stem which occurs in the xylem tissues of the tree when in leaf; nor does it occur because of root pressure forcing sap upward. According to the latest theory, it occurs because of the freeze-thaw cycle, which causes a decrease in pressure in the xylem tissues when gasses expand, which in turn draws water from surrounding cells and eventually from the root system and the soil (if unfrozen). Ice-compressed gases in the tissues force sap out of the stem as they expand in the sun and warmth. The sugar in maple sap is evidently stored in the xylem itself, rather than elsewhere. Another good source of technical information on maple syrup production is Ohio State U. Extension Bulletin #856. But, no mater how it is explained, it all comes down to cold nights and warm sunny days to produce sap flow in maple trees, and one must simply wait for that to happen.