New Zealand Journal of Botany abstracts
Arbuscular mycorrhizal fungal colonisation of Hieracium
lepidulum roots in experimental and field soil inoculated media
Theresa M. Downs*
Ian J. Radford†
Department of Botany
University of Otago
P.O. Box 56
Dunedin, New Zealand
*Present address: Department
of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand.
†Author
for correspondence. Present address: WA Conservation and Land
Management (CALM) Kununurra, PO Box 942, Kununurra, WA 6743, Australia.
ianra@calm.wa.gov.au
Abstract Recent comparative glasshouse experiments
have failed to isolate growth or competitive performance that would
explain invasiveness in Hieracium lepidulum in New Zealand. It
has been noted in a number of studies that root infection by arbuscular
mycorrhizal fungi (AMF) can alter growth and competitive performance in
invasive species. We therefore tested whether H. lepidulum plants
grown in experimental substrates (river sand and potting mix) were
infected with AMF, and compared AMF infection rates of these plants
with those of field collected and inoculated plants. AMF infection was
quantified at 100× magnification using a modified grid line
intersect method, following staining of root associated fungal
structures using trypan blue. In addition, plant establishment, leaf
cover, biomass, and root:shoot ratios of plants were compared to test
whether presence of AMF in roots was associated with changes in plant
performance. Very low AMF hyphal infection rates were found in H.
lepidulum roots from plants grown on river sand and potting mix
only, while c. 50% and 15% infection rate was observed in field
collected and field soil inoculated plants, respectively. The presence
of arum-type arbuscules confirms that observed non-septate hyphae were
AMF. Plant establishment, cover, and biomass (unfertilised pots only)
were greater in AMF infected plants, though this was possibly
confounded with soil addition effects. Future studies must separate
soil addition and AMF effects explicitly to determine whether growth
performance differences among AMF and non-AMF H. lepidulum plants
are directly related to the presence of the fungi.
Keywords Hieracium lepidulum; arbuscular
mycorrhizal fungi; infection; root associations
B05012; Received 4 April 2005; accepted 7 July 2005; Online
publication date 1 November 2005
New Zealand Journal of Botany, 2005, Vol. 43: 843–850
0028–825X/05/4304–0843 © The Royal Society of New Zealand 2005
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