Plant, Soil And Acacia

Plant Soil DOI 10.1007/s11104-012-1421-2

REGULAR ARTICLE

The dual symbiosis between arbuscular mycorrhiza and nitrogen fixing bacteria benefits the growth and nutrition of the woody invasive legume Acacia cyclops under nutrient limiting conditions
Peter E. Mortimer & Marcellous R. Le Roux & Maria A. Pérez-Fernández & Vagner A. Benedito & Aleysia Kleinert & Jianchu Xu & Alexander J.Valentine

Received: 15 February 2012 / Accepted: 6 August 2012 # Springer Science+Business Media B.V. 2012

Abstract Background and aims Acacia cyclops is an invasive species within Mediterranean ecosystems, characteristically low in soil nutrients. Thus associations with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhiza (AM) may provide an advantage to these legumes. This study investigatedthe role of AM and NFB in the growth and nutritional physiology of A. cyclops.

Methods Seedlings were inoculated with naturally occurring NFB, Glomus mosseae or both, and grown under glasshouse conditions for 5 months. Plants were cultivated in sand and supplied with a 20 % strength nutrient solution.Xylem sap nutrients, photosynthetic rates, biomass and chemical compositions, were recorded.Results The dual inoculation decreased the colonization of both symbionts, compared to a single symbiosis with

Responsible Editor: Hans Lambers. Electronic supplementary material The online version of this article (doi:10.1007/s11104-012-1421-2) contains supplementary material, which is available to authorized users. P. E. Mortimer (*) Key Laboratory of Biodiversity and Biogeography, KunmingInstitute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming 650201, China e-mail: petermortimer@mac.com P. E. Mortimer Center for Mountain Ecosystem Studies, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming 650201, China P. E. Mortimer : J. Xu World Agroforestry Centre, East Asia, 132 Lanhei Road, Kunming 650201, China M. R. Le Roux : A. Kleinert : A.J. Valentine Botany and Zoology Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa M. A. Pérez-Fernández Area de Ecología, Facultad de Ciencias Experimentales, University Pablo de Olavide, Cartera a Utrera, Km 1, 41013 Seville, Spain V. A. Benedito Genetics and Developmental Biology Program, Division of Plant and Soil Sciences, West Virginia University, 1090Agricultural Science Building, Morgantown, WV 26506, USA

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either symbiont. Despite low colonization levels, the dual symbiosis increased host biomass and relative growth rates. This was associated with increased photosynthetic rates and enhanced nutrition. Additionally, dual symbiotic plants had enhanced N and P acquisition and utilization rates. Xylem sap analysis showed higher levelsof NH4+ being exported from the roots to the shoots in the dual symbiotic plants compared with other treatments. Conclusions These findings suggest the dual symbiosis is an important factor in the growth and development of A. cyclops under nutrient limiting conditions. Keywords Arbuscular mycorrhiza . Nitrogen fixing bacteria . Dual symbiosis . P and N nutrition . Xylem sap . Invasive species .Acacia cyclops

Introduction Many of the Australian Acacia species are known to be invasive species within Mediterranean ecosystems, resulting in major losses of biodiversity from these sensitive ecosystems (Stock et al. 1995; Richardson et al. 1996; Marchante et al. 2003; Carvalho et al. 2010). Acacia cyclops A.Cunn. ex G.Don is one such species, occurring as a shrub or small tree in densethickets, especially along coastal areas where it was introduced to stabilize sand dunes (Richardson et al. 1996). Soils within these ecosystems are generally nutrient poor, characteristically low in N and P. These two nutrients are of specific importance to legumes, as nodule formation and the increased photosynthetic rates characteristic of symbiotic plants require increased levels of N and P. Thus,...