How does temperature influence AMF respiration?

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Arbuscular mycorrhizal fungi (AMF) are among the most widespread and ecologically significant of all soil micro-organisms. These soil fungi form symbiotic associations with around two-thirds of all land plants (some 200 000 species) in which both partners benefit. The plant obtains enhanced phosphorus uptake and other benefits such as increased pathogen resistance while the fungus receives a supply of carbon from its host plant. In addition, arbuscular mycorrhizal fungi (AMF) are known to influence plant community structure and nutrient cycling in natural ecosystems as well as releasing large amounts of respiratory CO2 into the surrounding soil, which ultimately diffuses into the atmosphere (contributing to the greenhouse effect). It is therefore surprising that we know relatively little about how this influential group of fungi respond to conditions in the environment. Temperature is one such key environmental variable because it effects metabolic processes, can show wide variation (i.e. day and night, winter and summer) and is predicted to increase as a result of global climate change. Although we do know how plants respond to variations in temperature, most studies on have been conducted using non-mycorrhizal (i.e. uncolonised) plants whereas in the natural environment AMF colonisation is the normal condition. In this proposal we will investigate how the AMF is influenced by temperature by measuring respiration. We will examine how AMF influence the respiration response of the plants root (compared to uncolonised roots). In addition, the AMF has two phases, one inside the root, and the other external to the root responsible for exploring the soil for nutrients. If both these phases respond to temperature in the same manner is currently unknown. We will vary the temperature experienced by the external phase independently of that of the plant so that the response of the AMF can be examined directly. We will also test if the fungus is able to adjust (i.e. acclimate) to changes in temperature such that respiration is maintained in a steady state rather than changing.