Occurrence of vesicular-arbuscular mycorrhiza in aquatic macrophytes from lakes and streams

This study reports the presence of vesicular-arbuscular mycorrhizae (VAM) in five of the 25 macrophyte species collected in lakes and four of the 24 species collected in streams. Four of the infected species in lakes, Littorella uniflora, Lobelia dortmanna, Elatine hexandra and Ranunculus flammula grew submerged whereas the fifth, Polygonum amphibium grew emergent on the shore. All the infected species in streams, Epilobium hirsutum, Veronica anagallis-aquatica, Myosotis palustris and Berula erecta grew emergent in the riparian zone. Among the infected species, isoetids had the highest degree of infection. The redox potential in sediments with non-infected specimen ranged from 54 to 280 mV and in sediments with infected species from 250 to 530 mV, indicating that the redox potential of the sediment might play a role in the development of VAM. Whether lack of infection was an inherent and species-specific trait was tested for one of the non-infected species Myriophyllum alterniflorum by transplanting plants to a population of infected L. uniflora. After 10 weeks, the Myriophyllum plants were heavily infected by VAM. The redox potential of the Littorella sediment was 500 mV compared to 160 mV of the Myriophyllum sediment, again indicating that the redox potential of the sediment might play a role for the development of mycorrhiza. (C) 2001 Elsevier Science B.V. All rights reserved.