Ecophysiological responses of endemic Cephalaria duzceensis to drought and salt stress

Endemic plants attract attention for their increasing potential for genetic biodiversity, an important phenomenon in all aspects of science. Little is known about the ability of the endangered Turkish endemic plant Cephalaria duzceensis to generate/remove reactive oxygen species or to adapt its biochemical responses in drought and saline environments. Consequently, changes in growth, relative water content (RWC), chlorophyll fluorescence (Fv/Fm), osmotic potential, hydrogen peroxide (H2O2) and proline contents, lipid peroxidation, and antioxidant enzymes were measured under drought (0, 5, 10, 15% PEG 6000) and salt (0, 75, 150, 225 mM NaCl) stresses. Salt-induced RWC, Fv/Fm, osmotic potential reduction, and lipid peroxidation were enhanced, suggesting that C. duzceensis is more sensitive to salinity than to drought. However, interestingly, growth increased under both. Although the increase in H2O2 content was greater under drought stress, aside from ascorbate peroxidase, no antioxidant enzyme activity increase was observed under salt stress. Conversely, the increase in peroxidase, ascorbate peroxidase, and catalase activity observed under drought may be related to the better growth performance, less Fv/Fm reduction, better water maintenance, and lower osmotic potential of C. duzceensis. These results strongly suggest that this endemic plant exhibits moderate drought tolerance and that salt stress has a more detrimental effect on C. duzceensis than drought stress.