Use of Nitrate Reductase Activity for Assessing Effectiveness of Mycorrhizal Symbiosis in Dorycnium pentaphyllum Under Induced Water Deficit

Abstract

The effects of arbuscular-mycorrhizal (AM) fungi, Glomus intraradices, Glomus mosseae or Glomus deserticola on root nitrate reductase (NR) activity, growth parameters, colonization rate and foliar nutrient (NPK) concentrations were assessed in Dorycnium pentaphyllum L. seedlings grown under well-watered (-0.03 MPa) or drought conditions (-0.60 MPa). Under water stress, plants colonized by AM fungi exhibited root dry weights and root/shoot ratios, which were lower than un-inoculated plants. G. deserticola had more effect on N uptake whereas G. intraradices and G. mosseae had more effect on phosphorus (P) uptake under the water-limited conditions tested. Nodulation was inhibited and AM colonization rate was increased by water stress in D. pentaphyllum seedlings inoculated with G. deserticola. Root NR activity increased significantly in G. deserticola-colonized plants, under both well-watered (by 137%) and drought-stressed conditions (by 140%), with respect to un-inoculated plants. NR activity could be used as an index for assessing the effectiveness of fungus-host plant combinations for mitigation of water-deficit stress.