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Centaurea ragusina L. is an endemic Croatian species morphologically well adapted to dry and sunny habitats. The effects of drought induced by 300 mM mannitol on relative plant growth rate, soluble peroxidase (POD) activity and isoperoxidase pattern in C. ragusina plants cultured in vitro were evaluated. Rooted plantlets originated from shoots grown in vitro on Murashige and Skoog half-strength (MS ½ ) medium supplemented with 2.5 mM indole-3-butyric acid. The plants were transferred to the same composition basal medium without or with 300 mM mannitol and harvested after 5, 10 or 15 days. Fresh weight, protein content, peroxidase activity and isoenzyme pattern in C. ragusina roots and shoots were analyzed. After 5, 10 and 15 days in stress conditions the relative plant growth was suppressed for 107, 79 and 52 %, respectively, in comparison to control plants. The content of soluble proteins in shoots and roots of treated and non-treated plants was similar, except after 10 days when it was elevated under water-stress conditions. Whether it was assayed with guaiacol or pyrogallol, drought significantly increased the peroxidase activity in both roots and shoots, especially after 10 days of stress conditions. Six different peroxidase isozymes were distinguished in shoots after 10 days of experiment. Two of these acidic (anioinic) isozymes were slow migrating and four fast migrating with much stronger intensity of the bands in drought-stressed plants. Also, drought induced presence of additional isozyme of slower migration towards anode thus confirming the culmination of stress after 10 days of experiment. These results suggest peroxidases to be important part of C. ragusina defense mechanism and their involvement in adaptation to stress conditions. |
