The pollen morphological diversity of Ziziphora clinopodioides (Lamiaceae)

Abstract

A cogent medicinal and aromatic plant, Ziziphora clinopodioides (Lamiaceae) is a perennial herb, its aerial parts is used as a wild vegetable or additive in foods to proffer pleasant aroma and flavour. There are many discussions about the intraspecific classification of this species and several subspecies have been introduced for it in different flora. These subspecies are morphologically very similar and identification of them is very difficult and in some cases, impossible. Therefore, in the present study, the pollen grains morphology of nine subspecies (32 specimens) of Z. clinopodioides were probed and documented in details utilising the scanning electron microscopy (SEM). In total, eleven pollen morphological characteristics were investigated and analysed by PAST software. The obtained results showed that pollen grains were hexacolpate and their equatorial views were sub-oblate to prolate. The exine ornamentation types of the pollen grains are bireticulate, microreticulate, reticulate and bireticulate-reticulate. The ANOVA test did not show significant difference for the studied quantitative traits. Although, the results of the multivariate analysis revealed a high diversity amongst the specimens even in the specimens of a single subspecies; it did not confirm the separation of subspecies in Z. clinopodioides.