Abstract

Mycorrhizal fungi co-evolved with the earliest land plants over 450 million years ago, in a symbiosis in which plants supply their fungal partners with sugars in return for mineral nutrients. As land plants evolved to form the first forests, proper soils developed and atmospheric CO2 was drawn down into ocean carbonate sediments accumulating as a result of increasing weathering of continental silicates containing calcium. However, until recently the role of mycorrhizal fungi in these transformations of biogeochemical cycles have gained little attention. I present new findings that demonstrate the importance of mycorrhizal fungi as potent agents of mineral weathering, driven by their access to 10-30% of plant photosynthate. This has led to a new paradigm recognizing mycorrhizal fungi to have played a major role in the evolution of the chemistry of the land, ocean and atmosphere since the advent of land plants, their effects intensifying through plant-fungal co-evolutionary advances progressively increasing carbon investment into these fungi. The length of mycorrhizal mycelia in contemporary ecosystems is now astronomical- being far greater than the distance across our solar system, and their importance as conduits of organic carbon flux into soils is now exploited by more than 10% of plant species through mycoheterotrophy.