Alleviation of salt stress in citrus seedlings inoculated with mycorrhiza: changes in leaf antioxidant defense systems

Citrus is a salt-sensitive plant. In the present study, the salt stress ameliorating the effect of arbuscular mycorrhizal fungi through antioxidant defense systems was reported. Three-month-old trifoliate orange (Poncirus trifoliata) seedlings colonized by Glomus mosseae or G. versiforme were irrigated with 0 and 100 mmol NaCl solutions. After 49 days of salinity, mycorrhizal structures were obviously restrained by salt stress. Mycorrhizal inoculation especially G. mosseae significantly alleviated the growth reduction of salinity. There were notably lower malondialdehyde and hydrogen peroxide contents in the leaves of mycorrhizal seedlings than in non-mycorrhizal ones. Mycorrhizal seedlings recorded notably greater activity of catalase and contents of ascorbate, soluble protein and glutathione under salinity or non-salinity conditions. The seedlings colonized by G. mosseae showed significantly higher antioxidant defense systems response to salinity than by G. versiforme. Our data demonstrate that mycorrhizal (especially G. mosseae) citrus seedlings exhibited greater efficient antioxidant defense systems, which provide better protection against salt damage.