DETECTION AND FEATURES OF WETWOOD IN QUERCUS-MONGOLICA VAR GROSSESERRATA

To elucidate the location of water in wetwood, variations in moisture content within a tree of Quercus mongolica var. grosseserrata were obs erved macroscopically by determination of moisture content and by soft x-ray photography. Then the typical wetwood, which had been precisely located by such macroscopic analysis, was examined further by cryo-sc anning electron microscopy. The moisture content varied considerably w ithin the tree trunk, and typical wetwood was detected in limited regi ons of the heartwood. The distribution of the wetwood did not always c orrespond to the discoloration of the wood. In the wetwood, almost all the lumina of vessels and fibers were filled with water, while the lu mina of ray and axial parenchyma cells were often cavitated. Intercell ular spaces produced by deformation of cell walls and radial shakes we re filled with water. In addition, tyloses were collapsed and torn in the wetwood, and they did not block the vessel lumina. These results-s uggest the possibility that vessels and fibers might serve as effectiv e pathways for the accumulation of water in the wetwood.