Interactions of assemblages of mycorrhizal fungi with two Florida wetland plants

Abstract Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their function in these environments. We conducted greenhouse experiments to study the effects of AM fungal assemblages—collected from different vegetation communities in a Florida wetland-under free-drained and flooded conditions, and at three phosphorus (P) levels on growth and P nutrition of Typha latifolia L. and Panicum hemitomon Schult. We also studied the effects of flooding on the spread of extraradical hyphae from P. hemitomon roots. For both plants no AM fungal assemblage had a consistent effect on plant growth and P nutrition. For T. latifolia , flooding nearly eliminated AM fungal colonization and, in the free-drained treatments, P amendment suppressed colonization. Furthermore, colonization by some mycorrhizal assemblages increased shoot- and root-P concentrations, but there were no significant plant growth responses. For P. hemitomon , the mycorrhizal association was suppressed by flooding and P amendment but, among the fungal assemblages, there were differences in root colonization. Mycorrhizal colonization improved some plant-growth and P-nutrition parameters at lower P levels relative to nonmycorrhizal controls, but generally conferred no benefit or was detrimental at higher P levels. Extraradical hyphae of most assemblages were restricted by flooding to 2.5 cm, though differences among AM fungal assemblages occurred with a maximum observed extension of 16.5 cm. We conclude that the impact of the mycorrhizal association on these wetland plants was a function of the complex interactions among the AM fungal assemblages, plant species, water condition, and P level. Future studies should focus on understanding the species composition of the assemblages, and potential adaptation to wetland conditions among these fungal species.