engleski

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

Centaurea ragusina L., an endemic Croatian species, grows in the gapes of vertical limestone cliffs along the Adriatic sea. It is primarily affected by drought and high light intensities and indirectly by salinity via seawater aerosol (Bačić et al., 1997). It was reported that salt stress may cause genotoxicity and induce DNA double-strand breaks in murine kidney cells (Kultz et al., 2001), but there is not such evidence for plant cells though. Also, whether it was caused by salinity or drought, osmotic stress usually affect cell division (Munns, 2002) in a negative manner. Considering that, the effects of NaCl and mannitol on mitotic index, chromosomal aberrations, chromatin abnormalities and spindle failure were compared. Rooted plantlets were transferred to liquid ½ MS (Murashige and Skoog, 1962) media containing IBA with different concentrations of NaCl (150 mM, 300 mM, 450 mM or 600 mM) and mannitol (300 mM). After ten days of stress conditions, root tips were fixed, hydrolysed, stained with Feulgen stain, macerated and squashed (Sharma and Sharma, 1972). Slides were freezed, stained with 5% Giemsa solution and mounted in Euparal. Mitotic index, mitotic and chromosomal abnormalities were analysed. Plants grown on media containing 150 mM NaCl showed significant increase of mitotic index and higher number of mitotic abnormalities compared to 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. References: Bačić T, Vladović D, Popović Ž. 1997. Contribution to knowledge about the leaf anatomy of the Croatian endemic taxon Centaurea ragusina L. subsp. ragusina. Nat Croat 4 ; 367-380. Kultz D, Chakravarty D. 2001. Hyperosmolarity in the form of elevated NaCl but not urea causes DNA damage in murine kidney cells. Proc Natl Acad Sci 98 ; 1999– 2004. Munns R. 2002. Comparative physiology of salt and water stress. Plant Cell Environ 25 ; 239-250. Murashige T, Skoog F. 1962. A revised medium for rapid growth and bioassay with tobacco tissue culture. Physiol Plant 15 ; 473-497. Sharma A K, Sharma A. 1972. Chromosome techniques: Theory and Practice. Buterworths and Co. Ltd, London.

osmotic stress; Centaurea ragusina L.; cytotoxicity

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