Plant-Mycorrhiza Percent Infection as Evidence of Coupled Metabolism
  A common feature of mycorrhizal observation is the growth of the infection on the plant root as a percent of the infected root or root tip length. Often, this is measured as a logistic curve with an eventual, though usually transient, plateau. It is shown in this paper that the periods of stable percent infection in the mycorrhizal growth cycle correspond to periods where both the plant and mycorrhiza growth rates and likely metabolism are tightly coupled. 
Reginald D. Smith