Field experiment on water transport of oak trees measured by computer tomograph and magnetic resonance imaging

Our multidisciplinary research group has been engaged in studying the water transport traced by short half life cyclotron produced isotopes (Na-24,K-43) for many years in oak species. There are a lot of different methods to estimate quantitatively the sap flow in trees. Most of these are indirect, producing relative data. Our isotope labeling technique is the only one, offering direct velocity values. To interpret these results however are very difficult because it is impossible to estimate sap now quantitatively without any information regarding the actual cross section through which this now is carried on. The computer tomograph and magnetic resonance techniques can provide exact and quantitative information about the areas with high water content within the trunk. The first results suggest that not only the outermost layer of xylem, but also the other water rich compartments might play a decisive role in sap flow. (C) 1998 Elsevier Science Ltd.