Water uptake in deciduous trees during winter and the role of conducting tissues in spring reactivation

Abstract

In winter, deciduous trees lack any means for transpiration, nevertheless their buds swell and increase in weight. It is known that vessels play an important role in spring reactivation and that phloem may be involved since buds fail to break when twigs are ringed. This study investigates water/nutrient translocation from winter until reactivation in spring for five North European species: maple (Acer pseudoplatanus L.), birch (Betula pendula Roth), alder (Alnus glutinosa Gaertn.), beech (Fagus sylvatica L.), and ash (Fraxinus excelsior L.). Accordingly emphasis is laid on the relative timing of onset of water conduction among the species. Beginning in late March, a continuous increase of water movement occurs in all the trees. However, this began earlier in birch and maple than in beech. In ash water uptake is delayed. Similar results were obtained with transpiration experiments. Delay of water conduction in ash is probably because ring-porous species depend on new conducting tissues to replace the previous year's nonfunctioning xylem. Analysis of three cations in buds showed that magnesium remained constantly low while calcium gave high values from the beginning. Potassium concentration rose and its accumulation correlated with water content/dry weight increase during bud development. Potassium thus indicated acropetal transport to the buds, since the spring sap showed the same tendency.