Mycorrhizal infection,phosphorus uptake,and phenology in Ranunculus adoneus: implications for the functioning of mycorrhizae in alpine systems

Phosphorus levels, phenology of roots and shoots, and development of vesicular arbuscular mycorrhizal (VAM) fungi were monitored for two years in natural populations of the perennial alpine herb, Ranunculus adoneus. The purpose of this study was to understand how phosphorus uptake relates to the phenology of R. adoneus and to ascertain whether arbusculus, fungal structures used for nutrient transfer, were present when maximum phosphorus accumulation was occurring. Arbuscules were only present for a few weeks during the growing season of R. adoneus and their presence corresponded with increased phosphorus accumulation in both the roots and shoots of R. adoneus. In addition, phosphorus accumulation and peaks in mycorrhizal development occurred well after plant reproduction and most plant growth had occurred. The late season accumulation of phosphorus by mycorrhizal roots of R. adoneus is stored for use during early season growth and flowering the following spring. In this way R. adoneus can flower before soils thaw and root or mycorrhizal nutrient uptake can occur.