Seed morphology of some Plantago (Plantaginaceae) species in Iran and its systematic and phylogenetic implications

Abstract

: Plantago is a cosmopolitan genus with approximately 200 species and various infrageneric classifications have been reported. In this study, the seed morphologies of 19 species of Plantago from Iran were studied and documented in detail using scanning electron microscopy and light microscopy. The studied species were grouped by using statistical analyses such as a minimum spherical cluster method based on Euclidean distance, principal coordinate analysis, and multidimentional scaling. We have described four types based on the seed shape and states of the inner side of the studied seeds: convex-angular type, convex-elliptic type, flat-elliptic type, and concave-elliptic type. In this study, three types of seed coat patterns were recognized: reticulate, scalariform to reticulate, and papillate. Regardless of the limited range taxa considered, our data convincingly support a close relationship between subgenera Plantago and Coronopus , and between Albicans and Psyllium . Consequently, we would suggest that the species of subgenus Coronopus should be placed within subgenus Plantago as Pilger’s taxonomy, and the species of subgenus Albicans should be merged within subgenus Psyllium as Rønsted et al.’s taxonomy. The seed morphology revealed that subgenus Plantago and subgenus Albicans are paraphyletic. Moreover, the deformation of testa cells can be an indicator for finding different lineages at series to the subgenus level. The features of the arrangement of testa cells and anticlinal walls can be used at the species level, especially when the morphological diversity between species is low. We conclude that seed morphology provides useful and important information on phylogenetic relationships of Plantago species, and thus they have systematic significance.