Cytogenetic effects of osmotic stress on the root meristem cells of Centaurea ragusina L.

Centaurea ragusina L. (Asteraceae), an endemic Croatian species developed xeromorphic characteristics which have arisen as a consequence of arid- and salt-affected environment. Cytogenetic effects of mannitol (300 mM) and different NaCl concentrations (150, 300, 450 and 600 mM) on root meristem cells of in vitro cultured C. ragusina were analysed after 10 days of stress conditions. Plants grown on media containing 150 mM NaCl showed significant increase of mitotic index and higher number of mitotic abnormalities as compared to those of control conditions. Although the mitotic index in control and mannitol-treated samples was almost the same, mitotic and chromosomal abnormalities doubled in the latter. Higher concentrations of salt (300, 450 and 600 mM NaCl) caused total inhibiton of mitotic activity in root-tip cells. Comparison of isoosmotic concentrations of salt (150 mM) and mannitol (300 mM) revealed more detrimental cytotoxic effect of mannitol and a certain tolerance of C. ragusina towards moderate salinity.