Inflorescence structure in species of Spartina Schreb. (Poaceae: Chloridoideae: Cynodonteae)

The typology developed by Troll was followed to describe inflorescence structures for 15 species of Spartina. In all species here studied, truncation of the terminal spikelet of the main axis and primary paracladium was observed. The truncation can also involve the short paracladia subzone so that the inflorescence is confined to just the long paracladia subzone. A great homogenization of paracladia and maximum ramification degree limited generally to the second order of branching are distinctive characteristics of the genus. Proximal paracladia with third-order branching were found in only three specimens, and in these exceptional cases, the homogenization is partial. Sometimes, in some species, a subzone of long and short paracladia can be distinguished. The absence of trophotagma paracladia in all the species studied was verified. The variation in the structure of the inflorescence among species is due to the differences in the number of short paracladia, long paracladia, total number of primary paracladia and also in the angle of divergence of the long paracladia from the main axis. The latter, in addition to variations in the intercalary growth of the internodes produces modifications in the general appearance of the inflorescences. The systematic and taxonomic value of the inflorescences in Spartina is discussed.