Drought Effects on Colonization of Artemisia Tridentata Seedlings by Arbuscular Mycorrhizal Fungi

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Student Presentation

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Marcelo Serpe


Arbuscular mycorrhizal fungi (AMF) are obligate biotrophs that facilitate nutrient uptake in exchange for organic carbon. Traditionally, the plant-AMF symbiosis has been considered mutualistic. However, various results indicate that the symbiosis can range from mutualistic to parasitic depending on the plant-fungus genotype involved in the association and environmental conditions. During severe drought, plants close their stomata, which limits carbon uptake. Under these conditions, AMF could become parasitic if the host plant cannot exclude the fungus. We investigated this notion in Artemisia tridentata seedlings inoculated with AMF spores of Rhizophagus irregularis. Seedlings were initially grown under well watered conditions. Subsequently some seedlings were kept well watered, while others experienced a gradual and terminal drought. The effects of drought on the seedlings were monitored weekly by measuring stomatal conductance and photosynthetic electron transport. When water-stressed plants showed negligible stomatal conductance and electron transport, water-stressed and well-watered plants were sampled and analyzed for AMF colonization. Total AMF colonization was 62 (±13) and 67 (±17) % for well watered and water stressed plants, respectively. Similarly, arbuscular colonization was 27 (± 4) and 27 (±11) % for well watered and water-stressed plants. The lack of significant differences in total and arbuscular colonization indicates that A. tridentata seedlings cannot exclude R. irregularis. This may lead to a parasitic symbiosis under severe water stress.

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