INVESTIGATIONS OF THE DELTA-C-13 PATTERN IN LEAVES OF FAGUS-SYLVATICA L

The natural abundance of 13C in different parts of beech (Fagus sylvatica L.) leaves was analysed. Values for leaf ribs were consistently higher than those for intercostal tissue. Similar differences occur between petiole and stem, with petiole being less negative. The pattern of results is the same, independent of the position in the tree. However, the absolute values differ by up to 6%. from the bottom to the top of the tree. Values of δ13C are in the range of - 29 to - 32%. for the lower leaf strata; while values between - 24 and - 26%. have been measured for the top of the tree. Absolute δ13C values of the whole tissue and cellulose differ by about 2%., but relative δ13C trends are almost identical. However, δ13C trends are not identical for different leaf parts. A comparison of cellulose and whole tissue δ13C data makes it unlikely that the δ13C variations are primarily due to different compositions of chemical compounds. No fractionation seems to exist between leaf and wood cellulose. Tissue from different areas of a leaf revealed identical carbon isotope compositions. © 1990 Oxford University Press.