Effects of Arbuscular Mycorrhizal Inoculation on Growth, Photosynthesis and Antioxidant Enzymatic Activity of Euonymus Maackii Rupr. Under Gradient Water Deficit Levels
Abstract The role of arbuscular mycorrhizal (AM) fungus (Rhizophagus intraradices) in amelioration of water deficit mediated negative influence on growth, photosynthesis and antioxidant system in Euonymus maackii Rupr. was examined. E. maackii seedlings were subjected to 5 water deficit levels: soil water contents of 20 %, 40 %, 60 %, 80 % and 100 % field capacity (FC) respectively, and 2 inoculation treatment: with and without AM inoculation. Water deficit increasingly limited seedlings growth of height, biomass accumulation of shoot and root, chlorophyll content, gas exchange and chlorophyll fluorescence parameters along the increase of water deficit level. In addition, Water deficit stimulated the activities of antioxidant enzymatic activities, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of both shoot and root, except under 20 % FC condition. E. maackii seedlings under all water deficit conditions formed AM symbiosis well with AM fungi, which ameliorated the drought mediated negative effect significantly, especially under 40 % and 60 % FC conditions. Under 40 % to 80 % FC conditions, AM formation improved seedlings growth and photosynthesis by significantly enhancing biomass accumulation, chlorophyll content and assimilation. Mycorrhizal seedlings showed better tolerance and less sensitive to water deficit, reflected in lower SOD activities of shoot and root, and CAT activity of shoot under 40 % and 60 % FC conditions. Down-regulation of antioxidant system in mycorrhizal seedlings suggested better maintenance of redox homeostasis and protection of metabolism, including biomass accumulation and assimilation. All the results advocated the positive role of R. intraradices inoculation in E. maackii against water deficit, which suggested the potential role of AM fungi in ecological restoration in arid region.