Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2006
Publication Date: 7/1/2007
Citation: Grigera, M.S., Drijber, R.A., Wienhold, B.J. 2007. Increased abundance of arbuscular mycorrhizal fungi in soil coincides with the reproductive stages of maize. Journal of Soil Biology and Biochemistry. 39:1401-1409. Interpretive Summary: Arbuscular mycorrhizal (AM) fungi are soil microorganisms that associate closely with the roots of many plants and play an important role in phosphorus acquisition using energy derived from plant roots. We used a chamber technique to measure AM fungi growth and soil phosphorus depletion during the grain fill stage of plant growth in corn. We found that AM fungi continued growth during the grain fill period and were therefore acquiring energy from the host plant. We also measured a reduction in phosphorus in chamber soil demonstrating that AM fungi were providing phosphorus to the host plant. The results document that AM fungi are active during the grain fill period and may benefit the corn crop by acquiring phosphorus.
Technical Abstract: Arbuscular mycorrhizal (AM) fungi are recognized for their positive effects on plant growth, playing an important role in plant P nutrition. We used C16:1cis11 and C18:1cis11 fatty acid methyl ester (FAME) biomarkers to monitor the dynamics of AM fungi during the reproductive stages of maize (Zea mays L.) grown at high yield in Nebraska, USA. Two fields with four different levels of P availability were sampled throughout the reproductive stages. Chambers, made of PVC enclosed mesh fabric to allow passage of roots and hyphae (+R) or hyphae alone (-R) and amended with either KH2PO4 (+P) or distilled water (-P), were installed in the field at tasselling and removed after three, six and nine weeks. Our objectives were (i) to provide evidence for C allocation to AM fungi during the reproductive stages of high productivity maize, and (ii) to link AM fungal growth dynamics with changes in soil P availability. We observed that initial AM FAME concentration was lower at sites with a high availability of P. During the reproductive growth of maize, AM biomarkers increased inside the chambers and were consistent with the biomarker increase observed in adjacent field soil. This confirms that there is C allocation from the plant to the symbiont during the reproductive stages of maize. We also observed a reduction in available P in +R and –R chambers. This observation implies that hyphae were as efficient as roots and hyphae in reducing the P concentration in chambers. These results demonstrate that AM fungi are active during the reproductive growth stages of maize and may benefit high productivity maize crops by facilitating P uptake.