Cytogenetic effect of prolonged in vitro exposure of Allium cepa L. root meristem cells to salt stress

Salt stress severely affects plant growth and regulation; however knowledge about its effect on cytological changes is limited. In this report, studies were carried out to reveal the morphological and cytogenetic responses of the Allium cepa roots after prolonged (7, 14, 20 days) exposure to salt stress in tissue culture conditions. Roots of plants were treated with different concentrations (100, 200, 300 mM) of NaCl and KCl added to the culture medium. Both salts caused root growth reduction and showed cytotoxic effect reflected in reduction of root tip cells mitotic activity and increase of different abnormalities such as chromosome breaks and bridges and formation of micronuclei. This experiment showed differences of the action of excessive amounts of both tested salts at the cellular level, as KCl induced higher frequencies of abnormalities during cell divisions, whereas NaCl showed more mitodepressive effect and more frequently led to the root meristem cell death.