What Have We Learnt from Studying Mycorrhizal Colonisation of Wetland Plant Species?
Wetlands are ecosystems where the water regime is the main factor that shapes the physical, chemical and biological characteristics. Wetland plants are rooted in water-saturated soils that are frequently anoxic. In spite of this, the rhizosphere can be oxygenated due to the aerenchyma of the wetland plants, which enable active ventilation of roots, rhizomes and the nearby rhizosphere. Some wetland species have an amphibious character, whereby they can thrive both in water and on dry land, with the development of structurally different aquatic and terrestrial forms. Studies of fungal colonisation in wetlands have revealed the presence of fungal endophytes and mycorrhizal fungi. These colonisers are affected by the hydrological regime of the specific wetland. The availability of oxygen also alters the morphology and density of the individual fungal structures. It has been shown that occurrence of arbuscular mycorrhiza is negatively correlated with water depth and duration of flooding. In wetlands, the availability of nutrients depends on a variety of factors, which can mask the role of these fungi. This is particularly the case for phosphorus, which is the main plant benefit from mycorrhizal symbiosis. The same holds true for the potentially positive role of aerenchyma, as the conditions that induce their development inhibit colonisation by arbuscular mycorrhiza. Studies carried out in an intermittent lake, Lake Cerknica, have revealed relatively high arbuscular mycorrhizal colonisation of amphibious species. This appears to be due to the low organic matter content and the low level of plant-available phosphorus in the rhizosphere. At the same time, the frequency of colonisation is lower in aquatic specimens. The impact of water level fluctuations and season on fungal root colonisation of the common reed Phragmites australis is reflected in an altered frequency and intensity of fungal colonisation. The structures of dark septate endophytes that might have a similar role in plants as arbuscular mycorrhiza under stress conditions are relatively frequent in this species.
KeywordsMycorrhizal Fungus Arbuscular Mycorrhiza Mycorrhizal Colonisation Wetland Plant Water Level Fluctuation
This study was supported by Slovenian Research Agency, through projects “Young researchers” grants no. 3311-03-831202 (2003-2007) and 1000-06310153 (2006-2013) and Plant Biology programme (P1-0212). This support is gratefully acknowledged.
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