Image: Dirk Redecker/UC-Berkeley
New fossils suggest that the cozy relationship enjoyed by green plants and fungi today may have originated nearly half a billion years ago. In fact, according to a report in today's issue of the journal Science, a primeval pas de deux with fungi may have given green plants a toehold on land.
Botanist Linda K. Graham of the University of Wisconsin and a student coaxed the new specimens out of sediments collected in Wisconsin that were dated to 460 million years ago. Unsure of exactly what they might be, they turned to fossil fungi expert Dirk Redecker, a postdoctoral researcher at the University of California at Berkeley, who identified the remains as the spores and rootlike threads, or hyphae (right), of fungi similar to those in the modern genus Glomus. The new fossils push the date for the earliest terrestrial fungi back by about 60 million years to the time when plants started taking over the land.
The vast majority of today's green plants form associations with so-called mycorrhizal fungi, which help them to absorb nutrients. Although the researchers did not find fossil green plants with the new fossil fungi, modern Glomus species are known to keep company with liverworts and hornworts--relatives of the only land plants present at the time of these fossils. And previously known fossils demonstrate that micorrhizal fungi were hanging around more advanced plants by 400 million years ago. Taking that into consideration, the researchers propose a similar partnership between the first land plants and the fungi represented by the new fossils.