The main purpose of the studies so far has been to get information about the seasonal changes of protein content and pinosylvin at the sapwood/ heartwood boundary. The studies have been performed on Scots pine trees sampled from a 50-year old stand located 70 km north-west of Umeå. Samples were taken every second week during spring to autumn 1996/97, and less frequently during the winter,from a total of 96 trees for the pinosylvin measurements and 14 trees for the protein analyses. The pinosylvin determinations were performed using FT-(NIR) Raman spectroscopy as described by Holmgren et al. (1999). The protein contents were determined by a HPLC method of amino acid-analysis frequently used at our laboratory.

Although the between-tree variations in the concentration of pinosylvin at the sapwood/ heartwood border were very large, almost all sampled trees showed a similar pattern. The key feature of this pattern was that the amount of pinosylvin increased considerably at the boundary zone between the sapwood and heartwood, i.e. in a band appr. 1 mm (ca. half an annual ring) from the border, which was visualised by staining. The amount of protein varied between ca. 1.5 and 2.7 mg/g d.w. There was great variation between trees in both pinosylvin and protein content, but it was not possible to trace a specific period during which heartwood was formed. The lack of changes detected in pinosylvin and protein amounts indicates that either there is no special period for heartwood formation, or that the methods used do not give sufficiently precise information about the period of heartwood formation.