Anatomy of Petiole in Polygonaceae

The present communication describes petiolar vasculature of eighteen species of Polygonaceae. It is always supplied by the median bundle of the ochrea along with some laterals and/or their upper branches. On the basis of the pattern of vascularization, they are put under seven categories. However, on the basis of their vascular organization, they are put under 12 categories. The petiole may be triangular or semi-circular in outline but ribbed in Rumex acetosa and R. nepalensis. The hypodermis is usually collenchymatous. It is chlorenchymatous in Rumex hastatus and Bilderdykia baldschuanica; collenchymatous below the ridges and chlorenchymatous below the grooves in Rumex acetosa and absent in Rumex arifolius and R. scutatus.Asclerenchymatous sheath is present just outside the bundles in six species. In Persicaria bistorta numerous tanniferous cells are present in place of the bundle sheath. Druses have been observed in ground tissue in some 14 species and medullary bundles in three species. It has been observed that nodes with less number of lacunae and leaf traces have fewer vascular bundles in the petiole. Similarly, multilacunar nodes have larger number of vascular bundles in the petiole and in some cases the medullary bundles too. The herbs and climbers have fewer bundles in the petiole whereas the robust species have more bundles as also the medullary bundles.