Systematic Study on Aristolochia (Aristolochiaceae) Native to Iran

Aristolochia (Aristolochiaceae) is composed of three native species in Iran as A. hyrcana, A. olivieri and A. bottae. These medicinal and toxic plants are considered as Irano-Turanian and Zagrosian elements. There are few anatomical studies in this genus. Due to the morphological similarities between these species, in the present study, an attempt is made to evaluate the distinctive value of anatomical and micromorphological traits. The anatomical structure of leaves, stems, and ovaries and micromorphological features of pollen grains, leaf indumentum, epicuticular wax and seed coat of 23 populations of Aristolochia species in Iran has been investigated in the present study. Anatomical features were evaluated by multivariate statistical analyses. Pollen grains are monad, symmetrical, isopolar and non-aperturate. Marginal status, orientation, density and size of epicuticular wax show variation between species studied. The shape, size and surface ornamentation of the seed coat are capable of delimitation of A. hyrcana and A. bottae. Results of the present study show that pollen grains, leaf epicuticular wax and seed coat micromorphology provide diagnostic characteristics to distinguish closely related Aristolochia species. We find that there is a high overlap between A. bottae and A. olivieri. A. hyrcana is different from the other two species in its anatomical structure. Some widely distributed Aristolochia species show hybridization that makes species delimitation difficult. The existence of subspecies levels needs further investigation.