Ancient Plant Survival Strategy Revealed in New Study

A new study, led by the University of Leeds with researchers from the University of Nottingham, has uncovered how a group of ancient plants survived the most severe mass extinction in Earth's history. The research was published in the journal Nature Ecology & Evolution.

The Permian-Triassic extinction event, which occurred around 250 million years ago, saw a dramatic rise in global temperatures, leading to the collapse of forests and the creation of barren landscapes.

The Adaptation That Saved a Species

Lycophytes, a group of small, vascular plants, survived by fundamentally changing how they performed photosynthesis. They conserved water and tolerated extreme heat by opening their stomata—the pores used for gas exchange—at night instead of during the day.

They stored captured CO₂ as an acid for use in daytime photosynthesis. Researchers believe this may represent the first use of this mechanism, which kept Earth's biosphere active by removing atmospheric carbon.

How the Discovery Was Made

The research team studied the evolutionary relationships of lycophytes and analyzed carbon isotopes in fossil plants from South China. Different types of photosynthesis leave distinct carbon isotope signatures in plant tissues, allowing scientists to infer ancient plant functions.

The analysis revealed that lycophytes from the extinction period showed noticeably different carbon isotope values compared to other plants. Furthermore, climate model simulations suggest these plants thrived in areas where surface temperatures likely exceeded 50°C (122°F).

Modern Context and Future Implications

Today, plants using a similar form of photosynthesis—known as Crassulacean Acid Metabolism (CAM)—comprise a small proportion of global vegetation, primarily found in hot, dry environments like deserts. Over 1,200 species of lycophytes still exist, with the greatest diversity in tropical regions.

Lead author Dr. Zhen Xu from Leeds' School of Earth and Environment stated: "Our results suggest that under future warming, plants with CAM photosynthesis traits could become far more important."

Dr. Xu added: "If the world experiences sustained extreme heat, plant communities may shift toward species that are better able to tolerate high temperatures and water stress."

Broader Significance of the Research

The study integrated paleontology, geochemistry, and climate modeling to understand how life adapted to a past climate catastrophe. Researchers say this multidisciplinary approach deepens our understanding of the Earth system's resilience to major climate perturbations.