Biosystematic relationships among Psathrostachys, Critesion and Hordelymus in Hordeinae (Poaceae) based on the anatomical characteristics of leaf blades

The anatomical characteristics of leaf blades of the major species of Psathyrostachys,Critesion and Hordelymus in Hordeinae were examined, their similarities and differences on the leaf blades were summarized, and the taxonomic significance of leaf anatomical features among them also were discussed. Furthermore, according to the evolutionary trends of anatomical characteristics of three genera, their evolutionary positions and relationships were inferred. The results showed that Psathyrostachys was the most primitive one among three genera, Critesion was slightly more advanced than the former, and Hordelymus was the most advanced of them; Psathyrostachys might produce immediately Critesion, whereas Hordelymus might derive immediately form Critesion. The biosystematic relationships of these three genera were corroborated by the evolutionary trend of trispikelet in the external morphology.   Key words: Critesion, Hordelymus, Psathyrostachys, biosystematic relationship, leaf anatomical characteristics.