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

Water distribution in green stems ofCryptomeria japonica D. Don was observed by soft X-ray photography. In the sapwood, much water was present and evenly distributed. In the intermediate wood (the white zone), little water was present. The intermediate wood appeared in all cross sections of the stem and separated the heartwood from the sapwood in the intertracheid water connection. 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 moisture 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 connection suggested that the presence of water in the heartwood was caused by rewetting of the tracheid lamina 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.