Figure 6.

Analysis of Cell Division Activity in Secondary Xylem Cells in Ptt IAA3m–Expressing Plants.

(A) Periclinal cell divisions. Total numbers of divisions were determined by counting mitotic cell divisions in samples of fusiform cambial cells of three different trees per transformed line and the wild type. For each tree, 500 cambial fusiform cells were examined. Bars represent the ratio of dividing cells and the total number of fusiform cells counted in one tree. The difference in periclinal divisions between the wild type and Ptt IAA3m line 6 was significant according to a Wilcoxon test (P = 0.0496).

(B) Comparison of anticlinal cell division activity in the wild type (T89) and transgenic hybrid aspen lines (6 and 15) expressing Ptt IAA3m cDNA. Cell divisions were counted in each of three individual plants per transformed line and the wild type. Each bar represents one tree and shows the number of anticlinal divisions in relation to the total number of cell files per section studied. A minimum of four sections were examined per tree. Ptt IAA3m line 6 was significantly different from the wild type according to a Wilcoxon test (P < 0.1).