Micromorphological observations on lemma and palea surface of Bromus (Poaceae) in Iran

Abstract

Bromus (Poaceae) includes more than 160 species of mesophytic and xerophytic grasses from temperate regions of the world, of which 39 occur in Iran. The genus is considered taxonomically problematic due to the occurrence of hybridization, variation in ploidy levels, and phenotypic plasticity. Moreover, morphological similarities make species delimitation difficult. It resulted in different taxonomic classifications proposed along the time. Thus, in order to contribute to a better understanding of the species of Bromus, 21 species from six different sections of Bromus occurring in Iran were evaluated micromorphologically. The abaxial surface of the lemma and palea of the lowermost florets were examined using Scanning Electron Microscopy (SEM). Twenty-three quantitative and qualitative characters were analysed using PAST software. Lemma characters such as shape of silica cells, cork cells, crown cells, outline of long cell wall, and long cell length, and palea characters such as shape of cork cells, silica cells, and outline of long cell wall were informative among species studied. In UPGMA clustering most species were aggregated according to the previously delimited sections demonstrating the taxonomic value of micromorphological features in the species studied. Two sections Bromus and Genea showed a close relationship whereas two sections Ceratochloa and Pnigma were placed in one cluster close to the cluster including section Boissiera. The only exception was B. japonicus which was resolved within cluster of sect. Genea, not in cluster of sect. Bromus.