Nucleated xylem fibres in some Indian herbaceous species

The xylem fibres retained their nucleus even after their secondary walls ha ve been laid down, in sixty species of twenty nine genera belonging to twel ve families. In both, libriform and fibre tracheids the nucleus was oval to oblong or fusiform shaped. Nonseptate fibres were uninucleate while septat e fibres had two to three compartments, accompanied by a nucleus in each co mpartment. Accumulation of starch in fibre lumina was a common feature in a ll the species studied. The xylem fibres in Pupalia lappacea has also revea led presence of rhomboidal crystals. Xylem fibres were characterised by thi ck lignified walls with a narrow lumen and tapering ends. Cells which were morphologically transitional between the fibres and axial parenchyma were a lso noticed in some species. Occurrence of nucleus in xylem fibres and its possible significance is discussed.