In a series of experiments, she had found that the outcome of mycorrhizal relationships varied depending on the climatic conditions in her growth chambers. Sometimes plants benefited more from the relationship, and sometimes less, a trait she terms ‘symbiotic efficiency’. If plants are hitched to an efficient mycorrhizal partner, they receive more phosphorus and grow more. Field was able to estimate how efficient mycorrhizal exchange would have been around 450 million years ago, when atmospheric carbon dioxide levels were several times higher than they are today.
