Simbiosis En 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 studyinvestigated the 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 chemicalcompositions, 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 andBiogeography,
Kunming Institute 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 Plantand Soil Sciences,
West Virginia University,
1090 Agricultural Science Building,
Morgantown, WV 26506, USA

Plant Soil

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 acquisitionand utilization rates. Xylem sap analysis showed
higher levels of 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. exG.Don is one such species,
occurring as a shrub or small tree in dense thickets,
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...