Comparative Anatomical Analysis of three Rumex L. Species (Polygonaceae): Stem and Leaf Cross-sections Study

Rumex species (Polygonaceae) have very similar morphological characteristics and are challenging to classify depending on the shape of fruits as a taxonomic key. Previous studies have proven the importance of anatomical and microscopic characteristics in finding diagnostic elements for identifying plant species. To our knowledge, there is a lack of studies on the leaf and stem anatomy of Rumex L. species. Therefore, this research aims to investigate the anatomical features of stem and leaf cross-sections of Rumex conglomeratus, Rumex chalepensis and Rumex pulcher grown wild in Syria. Fresh plants were collected from various regions during fructification stage. Fresh young parts of stems and leaves were taken and cross-sections were made manually and stained using iodine green - carmine double coloration. The colored cross-sections were examined using a light microscope. This research represents the first detailed anatomical study of leaf cross-sections in three species of Rumex L. grown wild in Syria. The results highlighted 12 qualitative and 10 quantitative features of stem and leaf cross-sections. Only the stem of R. conglomeratus contained calcium oxalate crystals. Papillary trichomes were only present on the leaves of R. pulcher. The shape of stem and leaf cross-sections, the number of vascular bundles in leaf cross-sections, vascular bundle’s diameter, parenchyma layers and thickness, and the number of collenchyma layers exhibited significant differences among the studied species and could be taxonomically important in their classification.