Morphology, wood structure and cell wall composition of rolC transgenic and non-transformed aspen trees

Morphology, wood structure and cell wall composition of 35S-rolC transgenic hybrid aspen (P. tremulaxtremuloides) were compared with non-transformed control trees. The transgenics are characterised by stunted growth, altered physiological parameters and light green leaves of reduced size. Histometric measurements revealed thinner fibre walls as compared to the controls. UV microspectrophotometry of individual wall layers did not reveal distinctive differences in the lignification of xylem cells, but in the extremely thin-walled fibres of the transgenics the secondary walls were less lignified as revealed by KMnO(4) staining in transmission electron microscopy. In the transgenics the formation of xylem cells was delayed and the differentiation zone reduced to only a few rows. Immunocytochemical analyses revealed the deposition of lignins in less differentiated xylem cells as compared to the controls. The first labelling of condensed lignin appeared in cell corners and of non-condensed lignin in secondary walls near cell corners during the deposition of S 1 polysaccharides. Because of alterations in the formation and differentiation of xylem cells, 35S-rolC transgenic aspen may be useful for studies on molecular factors controlling the differentiation continuum.