Plant-fungal interactions via Glomalin: A fungal protein that affects soil ecosystem cycling of C, N, P & S.
Maul, Jude*,1, Drinkwater, Laurie1, 1 Cornell University, Ithaca, NY
ABSTRACT- Little is known of the role plant species play in influencing accumulation of the fungal protein glomalin, even though it is composed of photosynthetically fixed carbon transferred directly to the fungi. Physical protection of soil structure by glomalin leads to soil aggregate stabilization. Aggregate stabilization in turn sequesters plant organic matter (OM) in recalcitrant pools and result in net OM storage in the soil. Differences in plant traits may affect rhizosphere accumulation of glomalin and explain in part, the differential stabilization of plant derived OM observed across plant species. We have quantified total annual deposition of glomalin in the rhizospheres of nine plant species, in addition we have quantified the proportion of C:N:P:S sequestered in the protein. We seeded nine C3 species of plants; grasses, legumes and other forbs into 2m2 microplots and maintained them weed-free for two years. Field site records indicate 50 yrs. of prior Maize monoculture, which has shifted the 13C/12C ratio of the standing glomalin pool to -15‰. Glomalin produced since planting of the nine experimental C3 plants exhibits a typical C3 13C/12C ratio of -27‰. We report; i) annual glomalin production across nine species using 13C/12C natural abundance techniques, ii) stoichiometric relationship of C:N:P:S in glomalin iii) calculated soil sequestration of C:N:P:S in the protein using current half-life estimates of glomalin, iv) quantification of plant traits that predict differences observed in annual glomalin deposition. Initial quantification of glomalin indicates levels of 0.5-1.0 (mg/g gdw soil) across the field site. Plant species differed in the proportion of biomass allocated in roots and shoots, 0.13 for Buckwheat to 1.70 for Triticale. Biomass values did not correspond to total root length, which ranged from 0.85 to 3.2 (m/g soil) and may be a predictor of plant-fungal carbon exchange. Our results suggest that glomalin is a significant sink of organic C:N:P:S in terrestrial ecosystems and plant species differentially regulate glomalin accumulation. These results identify a complex mechanism of long-term soil organic matter storage in part, controlled by plant species.
Key words: Plant traits, Glomalin, Organic matter, Fungi
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