Morphological Characterization of <i>Amaranthus palmeri</i> x <i>A. spinosus</i> Hybrids

Abstract

The growth of clones of seven <i> Amaranthus palmeri </i> x <i> A. spinosus </i> hybrids was compared to type specimens of <i> A. palmeri </i> and <i> A. spinosus </i> . The hybrids came from the field where they were originally discovered and clones of the type specimens and hybrids were established under greenhouse conditions and used to compare growth rates. <i> A. palmeri </i> had the highest growth rate and <i> A. spinosus </i> the lowest growth rate based on height, node counts, and dry weight accumulation. <i> A. palmeri </i> also had the greatest number of days to flowering and <i> A. spinosus </i> the fewest. Hybrids had intermediary growth rates and days to flowering, but differed from each other with regard to sex identity. The hybrids were either dioecious like <i> A. palmeri </i> or, if monoecious, had patterns unlike <i> A. spinosus </i> . Spine length and texture also varied in hybrids and some were without spines. Hybrid 16Ci was short compared to all others and had succulent leaves and stems, which easily separated from the plant body. These hybridizations resulted in morphologically distinct types with acquisition of physical traits intermediate to the type specimens which may drive evolution of these species.