Ten Egyptian Amaranthus L. species have been subjected to both petiole and stem anatomy in order to assist their taxonomic divisions. The petiole outlines can help in the identification of A. albus, A. blitoides, A. caudatus, A. hybridus and A. lividus where they lack two lateral extensions and the petioles T.S. are crescent, V-shaped or rotund. The presence or absence of secretory glands in the petiole T.S. and their numbers can differentiate some species. The type of vascular bundles in both petioles and stems divide the studied species into two groups, the first with closed collateral vascular bundles and the second with concentric amphivasal ones.
The studied characters have been analyzed using SYSTAT program and three dendrograms obtained [Farthest Neighbor (FN), Group Average (GA) and Nearest Neighbor (NN)] gathered A. spinosus and A. retroflexus in the three dendrograms, with the addition of A. viridis in (GA) and (NN). A. graecizans, A. lividus and A. tricolor came together in the three dendrograms, with the separation of A. lividus in (NN). The phylogenetic relationship using PAST program revealed that A. albus is monophyletic, while the rest of the studied species are paraphyletic. After 5 nodes the rest of the species separated into two categories, the first category split into two sub-groups after four nodes. The first sub-group included A. graecizans, A. hybridus and A. tricolor are coming near to each other, each in a separate clade. The four species met in the second sub-group consisting of A. lividus, A. retroflexus, A. viridis and A. spinosus, each in a separate clade. The second category gathers A. blitoides and A. caudatus after five nodes from the first one.
Key words: Amaranthus, Anatomy, Clustering analysis, Petiole, Stem, Taxonomy.
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