Figure 5.

Anatomical Analysis of Ptt IAA3m–Expressing Lines.

(A) Comparison of the stem diameter of the wild type (T89) and transgenic lines 6 and 15 expressing Ptt IAA3m cDNA. The diameter of three plants per clone of the wild type and transgenic lines expressing Ptt IAA3m cDNA was compared at different internodes. Transgenic lines display reductions in diameter compared with the wild type at all stages of development. Bars show average diameters (n = 5; error bars represent sd). The stem diameter of the Ptt IAA3m lines was significantly (P < 0.05) smaller than that of the wild type at all measured internodes covering early to late stages of wood development. All Ptt IAA3m–expressing lines showed statistically significant differences from the wild type (t test, P ≤ 0.01), apart from line 15 at internode 5 (P = 0.015).

(B) Comparison of the xylem-to-phloem ratio between T89 and lines expressing Ptt IAA3m cDNA. Xylem and phloem width was measured in anatomical sections from internode 25. Bars show average xylem:phloem ratios (n = 3; error bars represent sd). The differences between the wild type and Ptt IAA3m lines were found to be significant according to t tests (P < 0.1).