Physiochemical and antioxidant responses of the perennial xerophyte Capparis ovata Desf. to drought

Caper (Capparis ovata Desf.) is a perennial shrub (xerophyte) and drought resistant plant which is well adapted to Mediterranean Ecosystem. In the present study we investigated the plant growth, relative water content (RWC), chlorophyll fluorescence (F_V/F_M), lipid peroxidation (TBA-reactive substances content) as parameters indicative of oxidative stress and antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POX), catalase (CAT) and glutathione reductase (GR) in relation to the tolerance to polyethylene glycol mediated drought stress in C. ovata seedlings. For induction of drought stress, the 35 days seedlings were subjected to PEG 6000 of osmotic potential −0.81 MPa for 14 days. Lipid peroxidation increased in PEG stressed seedlings as compared to non-stressed seedlings of C. ovata during the experimental period. With regard to vegetative growth, PEG treatment caused decrease in shoot fresh and dry weights, RWC and F_V/F_M but decline was more prominent on day 14 of PEG treatment. Total activity of antioxidative enzymes SOD, APX, POX, CAT and GR were investigated in C. ovata seedlings under PEG mediated drought. Induced activities of SOD, CAT and POX enzymes were high and the rate of increment was higher in stressed seedling. APX activity increased on both days of PEG treatment, however, increase in GR activity was highest on day 14 of drought stress. We concluded that increased drought tolerance of C. ovata is correlated with diminishing oxidative injury by functioning of antioxidant system at higher rates under drought stress.