Abstract
In order to characterise the effect of ectomycorrhiza on Na+-responses of the salt-sensitive poplar hybrid Populus x canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na+ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcellular localisation of Na+ and Cl- in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na+ and Cl- concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na+ and increased supply with K+.
Highlights
Inappropriate irrigation practices and high evaporation in semi-arid regions result in salt accumulation in the soil destroying the land for plant production
Influence of salt stress on the formation of reactive oxygen species and antioxidative defences. Since both mycorrhiza (Gafur et al 2004) and salinity (Bolu and Polle 2004) can cause oxidative stress, we investigated whether mycorrhization would increase antioxidative systems in roots, thereby constituting a preformed defence mechanism
Empirical data have shown that in salt marshes, members of typical non-mycorrhizal plant families such as Armeria maritima and Salicornia europaea can be colonised by arbuscular mycorrhizal fungi, suggesting a possible role of these fungi in host salt tolerance (Hildebrandt et al 2001)
Summary
Inappropriate irrigation practices and high evaporation in semi-arid regions result in salt accumulation in the soil destroying the land for plant production. Worldwide, about 25% of the irrigated land is damaged by salt and that these areas are increasing In the humid climates of middle and northern Europe, salinisation of agricultural land is not a problem but application of de-icing salt in winter alongside roads results in the accumulation of sodium. Since excess salinity injures plants, control and removal of NaCl-damaged trees and re-planting causes enormous economic losses in the public sector. High salinity disrupts plant ion homeostasis leading to secondary effects such as oxidative stress, growth arrest, and even death (Zhu 2001; Tester and Davenport 2003; Munns 2005). Much less attention has been devoted to the analysis of salt-responses in tree species
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
