SEASONAL ANTIOXIDANT CAPACITY OF ASPHODELUS AESTIVUS BROT. ROOT TUBERS IN RESPONSE TO ARIDITY FROM DEGRADED MEDITERRANEAN ENVIRONMENTS

Asphodelus aestivus Brot. (Walter) is the dominant geophyte species on degraded areas of eastern Mediterranean Basin. Because it has a stress-tolerant strategy and it is a competitive ruderal. We studied the activities of antioxidant enzymes (ascorbate peroxidase, APX; superoxide dismutase, SOD; catalase, CAT) in the root tubers of A. aestivus from Bursa, Turkey over one year. There was a seasonal variation in antioxidant enzyme activities. The CAT and APX showed similar variation model in which the activity was highest in July (9.3 ± 2.7 units/mg protein and 141.9 ± 52.7 units/mg protein) and lowest in August (1.2 ± 0.6 units/mg protein and 14.5 ± 2.3 units/mg protein). The SOD activity increasing in summer months was reached up the highest level in late summer (297.6 ± 48.1 units/mg protein). The significant negative correlations were also found between enzyme activities and water contents of soils (P<0.05). The increased antioxidant enzyme activities in summer and late summer periods may be a protective and acclimation mechanism against drought stress. These results indicate that drought can induce enzymatic antioxidant defence system in A. aestivus and this system may help to this species to spread on degraded Mediterranean environments.