In this study, the pollen morphology of 22 Turkish taxa (12 of which are endemic) of the taxonomically complex genus Thlaspi L. sensu lato was studied with light microscopy (LM) and scanning electron microscopy (SEM). We found that the pollen of Thlaspi are usually bilateral symmetric and anisopolar. They are prolate, subprolate, perprolate or spheroidal, with the polar axis ranging from 14.13 to 28.36 µm and equatorial axis from 8.75 to 19.48 µm. Pollen are usually tricolpate, but some of them are 1–2- or 4-colpate. The ornamentation of pollen of the examined taxa is usually micro or macro reticulate, and rarely foveolate. The exine thickness ranges from 1.59 to 2.75 µm, and the intine thickness from 0.54 to 0.94 µm. As a result of this study, some of the pollen characters such as the sizes of pollen and colpus, ornamentation of exine, apocolpidium, and shape and diameter of amb are found to be significant morphological characters for taxonomic use.

In this study, anatomical characteristics of leaves and stems of 19 taxa of Thlaspi sensu lato, 9 of which are endemic to Turkey, were investigated in order to determine taxonomic relationships among the studied taxa. The anatomical characteristics of all taxa were determined and assessed using the cluster analysis and the principal component analysis. The transverse sections of the leaves and stems exhibited various diagnostic characters in terms of the pattern of epidermal cell and mesophyll layers, the number and size of vascular bundles, and the thickness of the cortex and endodermis. Important differences were detected in number, size, and index of stomata, and in epidermal cell wall structures in the adaxial and abaxial surfaces. The results showed that the compared anatomical characteristics among taxa are partially compatible with their sectional delimitation in their traditional rank in The Flora of Turkey and the East Aegean Islands. The results also point out that some taxonomic re-arrangements may be required.