Fungal Symbionts Alter Plant Drought Response
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PLANT MICROBE INTERACTIONS
Fungal Symbionts Alter Plant Drought Response Elise R. Worchel & Hannah E. Giauque & Stephanie N. Kivlin
Received: 16 October 2012 / Accepted: 5 December 2012 / Published online: 19 December 2012 # Springer Science+Business Media New York 2012
Abstract Grassland productivity is often primarily limited by water availability, and therefore, grasslands may be especially sensitive to climate change. Fungal symbionts can mediate plant drought response by enhancing drought tolerance and avoidance, but these effects have not been quantified across grass species. We performed a factorial meta-analysis of previously published studies to determine how arbuscular mycorrhizal (AM) fungi and endophytic fungal symbionts affect growth of grasses under drought. We then examined how the effect of fungal symbionts on plant growth was influenced by biotic (plant photosynthetic pathway) and abiotic (level of drought) factors. We also measured the phylogenetic signal of fungal symbionts on grass growth under control and drought conditions. Under drought conditions, grasses colonized by AM fungi grew larger than those without mycorrhizal symbionts. The increased growth of grasses conferred from fungal symbionts was greatest at the lowest soil moisture levels. Furthermore, under both drought and control conditions, C3 grasses colonized by AM fungi grew larger than C3 grasses without symbionts, but the biomass of C4 grasses was not affected by AM fungi. Endophytes did not increase plant biomass overall under any treatment. However, there was a phylogenetically conserved increase in plant biomass in grasses colonized by endophytes. Grasses and their fungal symbionts seem to interact within a context-dependent symbiosis, varying with biotic and abiotic conditions. Because plant–
Electronic supplementary material The online version of this article (doi:10.1007/s00248-012-0151-6) contains supplementary material, which is available to authorized users. E. R. Worchel : H. E. Giauque : S. N. Kivlin (*) Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA e-mail: [email protected]
fungal symbioses significantly alter plant drought response, including these responses could improve our ability to predict grassland functioning under global change.
Introduction Plant productivity is primarily limited by water availability in many ecosystems [1]. Climate change may exacerbate water limitation as models predict an increase in the intensity and frequency of droughts [2]. Plants respond to drought via three mechanisms: (1) by altering their phenology, (2) by avoiding water deficits through reduced evapotranspiration and increased root-to-shoot ratios, and (3) by tolerating water limitation by increasing cellular osmolite concentrations to improve water uptake [3]. In addition to the above-mentioned direct plant responses to drought, fungal symbionts can enhance plant drought avoidance and tolerance strategies [4, 5]. Plant species predominantly associate with arbuscular mycorrhizal
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