Acacia mangium Willd. is an economic species for pulp and paper industry. The growth of the young tetraploid A.mangium trees was more superior than that of the diploid trees. The present study deals with the effects of age and multiploidy on fiber characteristics in tetraploid and diploid species. They were compared and analysed using Franklin's method with hydrogen peroxide and glacial acetic acid treatment, the data were analysed from micromeasurements. With age increment, the fiber length in the diploid trees increased significantly( p<0 01). Similarly, the fiber length measured in the same year also showed decrease from bottom upward along with the growth of the shoot height. The tetraploid wood fibers were also compared and analysed with the diploid fibers. In the 1\|year\|old shoots, the tetraploid fiber was significantly longer than the diploid's ( p<0 01 ), Whereas the Cw/Cav (ratio of the thickness of cell wall and the cavity of cell)of the tetraploid fibers was significantly smaller than that of the diploid's( p<0 01 ). Moreover, regardless of the age, in the main leaf veins the tetraploid fiber length was, similar to that in the wood, sinificantly longer than that of the diploid's, and the Cw/Cav was also significantly smaller. It is thus suggested that the fiber characteristics measured in the main leaf veins, which is a much easy and safe procedure, could possibly be expected to obtain the same results in adult wood.
