Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2007
Publication Date: 7/1/2007
Citation: Grigera, M.S., Drijber, R.A., Shores-Morrow, R.H., Wienhold, B.J. 2007. Distribution of arbuscular mycorrhizal biomarker C16:1cis11 among neutral-, glygo', and phospho-lipids extracted from soil during the reproductive growth of corn. Journal of Soil Biology and Biochemistry. 39:1589-1596. Interpretive Summary: Arbuscular mycorrhiza (AM) fungi form close relationships with the roots of most land plants. The relationship between AM fungi and plants is thought to result in AM fungi acquiring energy from the plant and the plant benefiting from more efficient P acquisition. Details of the relationship between AM fungi and crops are incomplete. We compared size of three lipid fractions using chemical extraction with and without physical grinding of the sample. Grinding released lipids involved in energy storage and cell structure. Lipids unique to AM fungi increased during the growing season showing that there was transfer of energy from the plant to the fungi. Further studies are needed to determine how key lipid pools can be used to understand AM fungi dynamics.
Technical Abstract: Arbuscular mycorrhiza (AM) fungi form symbiotic relationships with the majority of land plants and are known for their positive effects on plant P acquisition and soil quality. The extramatrical growth of the mycelium is a key factor in nutrient acquisition by the symbiont. Identifying patterns in plant-fungi growth is necessary for understand how these symbionts operate in agroecosystems over time. The objective of this work was to study C partitioning in AM fungi in soil samples during the reproductive growth stage of maize (Zea mays L.). Chambers made of PVC enclosed with a 1 mm mesh fabric to allowed roots and hyphae passage amended with distilled water were installed in two sites at tasselling and removed after three, six and nine weeks in Nebraska. Soil samples were analyzed using ester linked fatty acid (EL-FAME) and chloroform-methanol extraction (CM-FAME) analysis. We also separated and analyzed the neutral (NLFA), glyco (GLFA) and phospho (PLFA) lipid fractions. We observed that AM fungi have resistant structures that are hydrolyzed only after the soil sample is roller-milled (RM). These particular structures were enriched of NLFA and GLFA C16:1cis11, but not PLFA, indicating that storage lipids and possibly membrane lipids are released by RM. EL- and CM-FAME C16:1cis11 increased later in the maize season, effectively showing the C allocation from the plant to the fungi under field conditions. We successfully utilized EL-FAME and CM-FAME C16:1cis11 to study the dynamics of AM fungi in soils under field conditions, however the C partition was not clearly shown by the different fractions. PLFA C16:1cis11 did not change over time or due to RM. NLFA C16:1cis11 increased by RM the sample; and did not change over time. GLFA C16:1cis11 increased over time and due to RM the sample. Further studies are needed to elucidate the role of GLFA C16:1cis11 in AM fungi.