Involvement of antioxidant enzyme and nitrate reductase activities during water stress and recovery of mycorrhizal Myrtus communis and Phillyrea angustifolia plants

In a greenhouse experiment, we studied the effect of inoculation with an arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck and Smith) or with a mixture of three AM fungi (G. intraradices Schenck and Smith, Glomus deserticola (Trappe, Bloss. and Menge) and Glomus mosseae (Nicol and Gerd.) Gerd. and Trappe) on root and shoot nitrate reductase (NR, EC 1.6.6.1.) activity, mycorrhizal colonisation, plant growth, nutrient uptake and superoxide dismutase (SOD) and peroxidase (POX) activities in shoots of Myrtus communis and Phillyrea angustifolia seedlings after well-watered, drought and recovery periods. The mycorrhizal inoculation treatments increased significantly the growth and foliar nutrients (N and P) of both species independent of the water regime. Drought reduced NR activity in roots of both species and in shoots of M. communis, although both species inoculated with the mixture of AM fungi reached values higher than non-inoculated plants and plants inoculated with G. intraradices. The mycorrhizal inoculation treatments decreased significantly POX and SOD activities in shoots of both species. POX and SOD activities in inoculated P. angustifolia seedlings hardly varied during the drought and recovery periods. SOD activity was enhanced by drought in non-AM plants of both species and in inoculated M. communis, but to a lesser extent than in control plants.