Comparative anatomical studies on some species of the genus Amaranthus (Family: Amaranthaceae) for the development of an identification guide

A study of anatomical features of mature leaves and stems (at fruiting stage) of 12 Amaranthus taxa (Family: Amaranthaceae) shows high variation between them and supplied new characters. The internal structures were evaluated to clarify their effectiveness in solving taxonomic complexity and identification difficulty in this genus. Observation of the transections of blades showed that the epidermis is uniseriate, ground tissue consists of angular collenchyma and thin parenchyma. The vascular bundles shape has three patterns crescent, ring, ovate. Also they may be united or separated while the midrib shape in cross section has two patterns in which U-shaped, cordate or crescent bundle occurs. All leaves are petiolate. The examination of the petioles exhibits new and varied characters such as petiole shape (cross section), vascular bundles (shape, number, arrangement). While the resulted characters from the observation of the stem structure showed less variation. Nineteen qualitative characters with 38 character states resulted from leaf anatomy. Only (8) characters were sufficient to generate an identification anatomical key. DELTA program was used in key-generation. Also different measurements were carried out by a photo analysis program (Image J), such as lamina thickness, mesophyll thickness, area of upper and lower epidermal cells and thickness of upper and lower epidermal cells to exhibit most possible dissimilarities between the studied species.