Sample discs were taken at approximately breast height from 11 trees, of known age and management history, representing 6 species of Acacia (A. erioloba, A. fleckii, A. karroo, A. nilotica, A. tortilis and Faidherbia [Acacia] albida). The trees came from Zimbabwe, Malawi, Kenya and Somalia. Radial cross sections of wood were examined for growth rings, which were apparent in most species as narrow bands of marginal parenchyma filled with long crystal chains. The number of bands formed annually corresponded to the number of peaks in rainfall distribution. Samples from specimens of African Acacia species from the Oxford Forestry Institute's xylarium (FHOw) were also examined for similar crystalliferous chains, which were generally present. These results suggest that marginal parenchyma bands and crystalliferous chains define growth phases in African Acacia species, and may therefore be useful for age determination.
Gourlay, I.D.; Kanowski, P.J. Marginal parenchyma bands and crystalliferous chains as indicators of age in African Acacia species. IAWA Bulletin (1991) 12 (2) 187-194.