Soft X-ray observation of water distribution in the stem of Cryptomeria japonica D-Don I: General description of water distribution

Water distribution in green stems of Cryptomeria japonica D. Don was observ ed by soft X-ray photography. in the sapwood, much water was present and ev enly distributed. In the intermediate wood (the white zone), little water w as present. The intermediate wood appeared in all cross sections of the ste m and separated the heartwood from the sapwood in the intertracheid water c onnection. Maldistribution of water was generally observed in the heartwood , and three types of water presence were distinguishable: a "wet area" with accumulated water, a "dry area" with little water, and a "moderate moistur e area" with intermediate accumulation. The distribution pattern and amount of water in the heartwood varied dramatically among and even within trees. Separation of the heartwood from the sapwood in the intertracheid water co nnection suggested that the presence of water in the heartwood was caused b y rewetting of the tracheid lumina that occurred after heartwood formation. The maldistribution of water in the heartwood suggested that a difference in the process of rewetting causes both uneven distribution and the various types of water presence.