Stem anatomical survey of the genera Matricaria and Tripleurospermum (Asteraceae) from Turkey with its taxonomical and ecological implications

A comparative anatomical study of the stems in 32 taxa assigned in the two related genera; Matricaria (4 taxa) and Tripleurospermum (28 taxa, 30 accessions), was carried out in Turkey by using cluster analysis (CA) and principal component analysis (PCA) to address generic classification and taxa delimitation. All the studied taxa have the following stem characteristics: one layer of epidermal cells with a sparse distribution of non-glandular trichomes, a cortex composed of interchanging collenchyma and chlorenchyma cells, a number of schizogenous secretory ducts near the bundles, ovate to oblong and open collateral vascular bundles which are arranged in a ring and are variable in size, and parenchymatous pith. The differences among the taxa are mainly the thickness of the xylem in the vascular bundle, the length of the epidermal cells and the pith cell size. The taxonomic and ecological values of the anatomical data are discussed in light of the current framework.