The potential application of the foliar anatomy to identify of the Euphorbia species was evaluated by light microscope. The purpose of the present study was to investigate the leaf anatomical properties of Euphorbia in NE Iran and to evaluate their systematic importance. A comparative anatomical study of leaf blade of 24 Euphorbia taxa was prepared. This study revealed these taxa show variable in different tissues in leaf structure and they can be used as an instrument to solve some taxonomic problems more at subgenus and section levels and even at species level. The foliar limb structure differed in leaf symmetry, midrib outline, collenchyma cell rows in inferior surface, palisade cell rows both in superior and inferior surfaces, presence or absence bundle sheat. The different anatomical characters also indicated adaptation of this genus to changing ecological conditions and environmental factors, but we can not find any correspondence among them based on the variations in internal structure.

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