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, trading soil nutrients for plant sugar. The tufts are preserved cell by cell in a 407-million-year-old Scottish chert, and they are indistinguishable from the ones living plants make 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. The deal is older than the plants, not invented by them.

Dating & uncertainty

The Rhynie chert of Scotland preserves the partnership in cellular detail at about 407 Ma. Molecular dating places the origin of arbuscular mycorrhizal fungi near 480 Ma, and the earliest land plants may have partnered with a different fungal group entirely.

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