Antioxidant enzyme activities in shoots from three mycorrhizal shrub species afforested in a degraded semi-arid soil

Mycorrhizae may help plants to thrive in Mediterranean semi-arid ecosystems by altering antioxidant enzyme activities. Our objective was to determine the influence of mycorrhizal inoculation with an allochthonous arbuscular mycorrhizal (AM) fungus, Glomus claroideum, Schenck & Smith, or with a mixture of native AM fungi, on the activity of antioxidant enzymes from shoots of Olea europaea L. ssp. sylvestris, Retama sphaerocarpa (L.) Boissier and Rhamnus lycioides L. seedlings afforested in a degraded Mediterranean semi-arid soil. One year after planting, shoot biomass of inoculated O. europaea seedlings was about 630%, of non-inoculated plants. Shoot biomass of G. claroideum-colonized R. sphaerocarpa was greater than that of seedlings inoculated with the mixed native AM fungi after 12 months. Inoculation with a mix of native AM fungi was the most effective treatment for increasing shoot biomass and N, P and K contents in shoot tissues of R. lycioides. Both mycorrhizal inoculation treatments increased the nutrient contents in shoots of O. europaea and R. lycioides. In O. europaea plants, the inoculation treatments increased catalase, ascorbate peroxidase and dehydroascorbate reductase activities, but not monodehydroascorbate reductase and glutathione reductase activities. Inoculation with G. claroideum increased the activities of all antioxidant enzymes in R. sphaerocarpa. Monodehydroascorbate reductase, glutathione reductase and superoxide dismutase activities in R. lycioides leaves were preferentially increased by inoculation with the mixture of native AM fungi. This work support the view that increased antioxidant enzyme activities could be involved, at least in part, in the beneficial effects of mycorrhizal colonization on the performance of shrub species grown under semi-arid Mediterranean conditions.This research was supported by the EC + CICYT cofinanced FEDER programme (REN 2000– 1724-CO3-01)Peer reviewe