52-million-year-old symbiosis in amber discovered

Researchers find early evidence of community of fungus and tree

Ectomycorrhizae in Indian amber © Uni Göttingen
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Göttingen geobiologists have discovered in a 52-million-year-old Indian amber early evidence for a still occurring form of symbiosis between fungi and plant roots, the so-called mycorrhizas. The mycorrhizae seem to have played a significant role in the early tropical rainforests of Earth's history, the researchers write in the journal New Phytologist.

Mycorrhizae are a widespread form of cohabitation between soil fungi and the roots of certain plants. The fungus comes into contact with the root system of the host plant, increases with its filamentous cells, the root surface of the plants and thus supports their food intake. In return, the plant supplies energy to the fungus in the form of sugars. Produced with these sugars

Mushroom the substances necessary for its growth.

Ectomycorrhizae: a special kind of fungus-plant symbiosis

The scientists of the Courant Research Center Geobiology of the University of Göttingen have now found for the first time fossil mycorrhizae, which are associated with flowering plants - plants whose ovules are enclosed in an ovary. This is a special type of fungus-plant symbiosis, the so-called ectomycorrhizae.

In this form of symbiosis, the fungus does not penetrate into the root cells of the plants. The amber inclusions found reveal different stages of development and provide insights into various morphological details. "The fossil resin - the amber - was produced by trees from an early tropical rainforest, " explains Alexander Schmidt from the Courant Research Center Geobiology. "Mycorrhizal findings in fossils are extremely rare. In fact, only one other fossil of ectomycorrhizae has been discovered so far. "Display

Acquisition of the mycorrhizal surface with a scanning electron microscope. Uni G ttingen

Mycorrhizal system released from fossil resin

In collaboration with Indian palaeontologists and the American Museum of Natural History in New York, the scientists managed a detailed processing of the fossils. "The Indian amber differs significantly in its chemical composition from the Baltic amber of the Baltic Sea region and can easily dissolve in organic solvents, " explains Christina Beimforde, specialist f Fossr fossil mushrooms at the Courant Research Center.

This peculiarity enabled us to release one of the mycorrhizal systems from the fossil resin. By means of ultrastructural analyzes under a scanning electron microscope, we were able to study this specimen as meticulously as we do today. In further investigations, the organic constituents of the fossilized fungus-plant community have been analyzed. For example, researchers have for the first time detected the black dye melanin in fossil fungi.

Key innovation in the evolution of plants

More than 400 million years ago, mushrooms supported the plants in the conquest of the mainland this cohabitation is considered a key innovation in the evolution of plants. According to the scientists, the 52-million-year-old amber find is further evidence of the morphological stability of mycorrhizas, which also play an important role in today's ecosystems. (New Phytologist, 2011; DOI: 10.1111 / j.1469-8137.2011.03868.x)

(University G ttingen, 14.11.2011 - DLO)