ABSTRACT

Amaranthus (Amaranthaceae) is a genus of tropical origin but widely distributed all over the world, including temperate regions. About 50 species are native to the Americas and another 15 can be found in Europe, Asia, Africa, and Australia. Most amaranth species are pioneer nitrophilous annuals of open habitats and produce many small dormant seeds. Amaranths are herbaceous annual plants, with prostrate or erect stems, that may reach 2 m height. Different morphological types of grain amaranth have been described according to their branching pattern, height, inflorescence size and form, days to maturity, seed size, and color. Amaranthaceae plants are characterized by anomalous secondary thickening of the stem, in which phloem is present within the secondary xylem. Information on root morphology and spatial distribution in the soil, as well as its responses to nutrient and water availability, are of primordial importance for crop management and yield improvement.