engleski

Morpho-anatomical and physiological responses of Centaurea ragusina L. to salinity

To elucidate the physiological basis of salt tolerance in the Croatian plant species Centaurea ragusina L., the accumulation of salt ions and proline, functioning of photosystem II as well as the changes in the antioxidative system was studied. Plants were subjected to either salt (150, 300, 450, 600 mM NaCl) or mannitol (300 mM) treatments for two weeks. Effects of iso-osmotic concentrations of NaCl (150 mM) and mannitol (300 mM) were compared in order to discriminate possible differences in C. ragusina response to ionic (NaCl) and osmotic (mannitol) components of salinity. C. ragusina plants, especially leaves, accumulated Na+ and Cl- as a predominant osmotica - the concentrations of leaf Na+ and Cl- at 300mM NaCl treatment were 90- and 10-fold greater, respectively, than those measured in controls. Simultaneously, significant reductions in plant K+, Mg+ and Ca2+ concentrations occurred. In addition, lower salt concentrations induced leaf succulence which was accompanied by increased leaf relative water status, vacuole volume and cell expansion. Regardless of significant accumulation of proline, 600mM NaCl- and mannitol-induced osmotic stress markedly decreased relative water content and caused plazmolysis in C. ragusina leaves. Given the suppressed levels of some photosynthetic proteins and down regulation of photosystem II efficiency, both stressors impaired photosynthesis though NaCl to a much lesser extent. Activities of SOD, CAT and APX in salinized plants seem to play an essential protective role in the scavenging processes. In spite of induction of antioxidative defense, mannitol and higher salt treatments caused oxidative damage to lipids and proteins as evident by carbonyl content and lipoxygenase activity. Presented data confirm better adaptation of C. ragusina plants to salinity than drought, indicating its tolerance toward salinity through ion accumulation.

C. ragusina; salinity; photosynthesis; antioxidants

nije evidentirano