LIFE × EVOLUTION

The Partnership Under the Soil

~407 million years ago

Phanerozoic · Paleozoic · Devonian

Fungal threads grew into the cells of the earliest land plants and branched inside them into fine bushy tufts, the structures through which living plants and fungi trade soil nutrients for sugar. The fossil tufts sit inside their host cells in a 407-million-year-old Scottish chert, and in shape they cannot be told apart from the ones formed in living plants today. Four hundred million years later, most plants on Earth still strike the same bargain.

Why it matters

The first plants had no roots worth the name; the fungi were their roots. Which fungi is a live question, and it matters: the earliest land plants appear to have partnered with a group nobody had suspected, and the familiar partners of today's plants only take over later. Fungi were on land before plants were, and their partnership probably helped the plants follow.

Dating & uncertainty

The Rhynie chert of Scotland preserves the partnership in cellular detail at about 407 Ma, which gives it no more than a minimum age. Molecular dating puts the origin of arbuscular mycorrhizae near 480 Ma, and the earliest land plants may have partnered with a different fungal group altogether.

Sources

1. Remy et al. (1994), PNAS · Four hundred-million-year-old vesicular arbuscular mycorrhizae
2. Bidartondo et al. (2011), Biology Letters · The dawn of symbiosis between plants and fungi
3. Lutzoni et al. (2018), Nature Communications · Contemporaneous radiations of fungi and plants linked to symbiosis

Earth history as one day

21:50:542 h 9 min before midnight

if Earth’s 4.54 billion years were compressed into a single day