CALCIUM OXALATE CRYSTALS IN SOME SPECIES OF THE TRIBE CARDUEAE (ASTERACEAE)

Calcium oxalate (CaOx) crystals in the tissues and organs of 18 species that belong to tribe Cardueae (Asteraceae), Arctium minus, Carduus candicans, C. nutans, C. pycnocephalus, Cirsium arvense, C. creticum, C. vulgare, Jurinea consanguinea, Silybum marianum, Tyrimnus leucographus, and Xeranthemum annuum within the subtribe Carduinae and Carthamus dentatus, C. lanatus, Centaurea cyanus, C. diffusa, C. iberica, C. salonitana, and C. solstitialis within the subtribe Centaureinae, were investigated, and their morphologies and distribution were determined using light microscopy. Two morphological types of crystals, styloids and prismatics, were the most commonly found crystals in the species examined. Raphides were only observed in the stem cortex and pith parenchyma cells of S. marianum, while druses were only viewed in the stem pith cells of C. pycnocephalus. Styloids were observed (if present) in the leaf, corolla, anther, filament, and style tissues. Prismatic crystals were common in almost all ovaries of the species investigated except Xeranthemum annuum which was found to include styloids in its ovary cells. Prismatics, styloids, raphides, and druses were present in the stems of the species. It is considered that crystal formation within the cell is under genetic control. Thus the type, and presence or absence of crystals may be represented as a taxonomic character. In conclusion, it is suggested that the type and location of CaOx crystals in the Cardueae constitute a diagnostic character and they may have taxonomic significance in this tribe.