IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Wednesday 30 November 2011
Concurrent Session 14 – Cyanobacteria & other organisms
1600 - 1740
Authors: Cuddy, W. S. 1 , Forster, B. 2 , Deaker, R. 3 , Summerell, B. A. 4 , Neilan, B. A. 1 ,Gehringer, M.
M. 1
1 . School of Biotechnology and Biomolecular Sciences, University of New South Wales,
Sydney, 2052, New South Wales.
2. Research School of Biology, Plant Sciences Division, Australian National University,
Canberra, 0200, Australian Capital Territory.
3 . Faculty of Agriculture, Food and Natural Resources, University of Sydney, Sydney,
2006, New South Wales.
4. Science and Public Programs, Botanic Gardens Trust, Sydney, 2000, New South
Wales.
Presentation Title: Cyanobacterial salt physiology and their impact on wheat seedling salt tolerance
Presentation Time: 1640 – 1700
Nitrogen-fixing cyanobacteria have been identified in soils and biological soil crusts worldwide. Understanding
their potential to support cereal growth, particularly under adverse conditions, is of great interest to crop
management and breeding. We assessed the potential benefits of cyanobacteria on growth of wheat seedlings
under salt stress. First, three cyanobacterial isolates from wheat fields: a heterocyst-producing Nostoc sp., a
Microcoleus vaginatus and a Leptolyngbya sp. were cultured in salinised medium at 5 and 15 dS m -1 and
sampled at mid-exponential and stationary growth phases to determine photosynthetic and nitrogen fixation rates
using Pulse Amplitude Modulation (PAM) fluorometry and Acetylene Reduction Assays (ARA), respectively.
These isolates were then established as soil crusts on sterilized sand into which germinated wheat seeds were
planted 1 cm below the surface. Sodium chloride was applied to generate salt stress with electrical conductivities
(ECe) of 6 and 13 dS m -1 . Pots were watered to field capacity daily, and the electrical conductivities monitored
during seedling development for either 14 days at 6 dS m -1 or 21 days at 13 dS m -1 . Quenching analysis using
PAM fluorometry was done on wheat leaves before sampling. Inductively Coupled Plasma-Optical Emission
Spectroscopy (ICP-OES) was conducted on separated root and shoot material. Both the Nostoc and the nonheterocystous
cyanobacteria Microcoleus vaginatus isolates fixed nitrogen at 8 and 6 n moles C2H4 μg Chl a -1 h -1
respectively, without affecting photosynthetic efficiency. The cyanobacterial soil crusts induced significant effects
on root and shoot nutrient concentrations, impairing plant salt tolerance. This study provides new evidence for
the ability of Microcoleus vaginatus to fix nitrogen, which suggests its contribution to soil ecology may currently
be undervalued. We were able to demonstrate that the cyanobacterial isolates used in this study in fact
enhanced the salt stress of wheat seedlings, thereby decreasing plant growth.
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2011