Radial variation of earlywood vessel lumen diameter as an indicator of the juvenile growth period in ash ( Fraxinus excelsior L.)

Abstract

In this study, it was determined that the radial variation of early vessel lumen diameter and the frequency of the vessel occurrence is limited to the zone adjacent to the pith and thus to the juvenile wood zone of stem cross-sections. The diameter of early vessel lumina increases along with the cambial age of annual growth rings up to approximately the 30th growth ring, while the frequency of the early vessel occurrence decreases. The width of the juvenile wood zone, determined on the basis of the curves of the early vessel lumen diameter gradient, comprises about 30 growth rings. Moreover, the juvenile wood zone can be further subdivided into the immature wood sub-zone (from the pith to the 15th growth ring) and the mature wood sub-zone (from the 15th to the 30th growth ring).