The significance of morphological and anatomical investigation of leaves and stems for the identification of Zygophyllaceae.

Background: In this study we examined morphological and anatomical variation in stem and leaf tissue of three genera in the Zygophyllaceae: Fagonia (4 taxa), Tetraena (4 taxa), and Tribulus (4 taxa) were investigated. Results The twelve examined taxa included nine species that grow in eastern region of Saudi Arabia. Additional features for taxon identification and characterization were developed as a result of our observations. We recorded stem diagram, epidermal cell shape, cortex, pith, the number of vascular bundles, petiole and blade outline in cross section, mesophyll type, and secretory and crystal distribution. Conclusions We conclude that anatomical features, particularly the petiole and blade outlines and the type of vasculature in the stem and petiole, are significant for identifying and distinguishing between the species examined here. A bracketed key is provided for the identification of the investigated taxa based on the characters analyzed here. The characters assessed in this study agreed with previous classifications of Zygophyllaceae species.