The survival of lycophytes during Earth's Permian-Triassic mass extinction, known as the "Great Dying," is a fascinating tale of biological innovation and resilience. This ancient plant group, characterized by their spore-bearing vascular systems, has captivated researchers at the University of Nottingham and the University of Leeds. Their study, published in Nature Ecology and Evolution, reveals a unique adaptation that allowed lycophytes to thrive in a scorching, carbon-rich environment. By employing a specialized form of photosynthesis called CAM (Crassulacean Acid Metabolism), these plants conserved water and tolerated extreme heat by opening their stomata at night, storing CO2 as an acid for daytime photosynthesis. This mechanism, the researchers suggest, may have been a crucial innovation that kept Earth's biosphere active, helping to combat the effects of global warming during the extinction event. While CAM photosynthesis is now rare, comprising only a small fraction of global vegetation, it is most prevalent in hot and dry environments like deserts. The study's findings have broader implications, indicating that plants with CAM photosynthesis traits could become more significant in the face of future warming. This raises a deeper question: How might our understanding of plant adaptation inform our strategies for addressing climate change? The research also sheds light on the evolutionary relationships of lycophytes, with quillworts, found worldwide, being their closest relatives. By studying carbon isotopes in fossil plants from South China, the team identified distinct isotopic signatures during the Permian-Triassic extinction period, which disappeared as environmental conditions improved. This discovery highlights the extraordinary thermal tolerance of lycophytes, with fossil evidence suggesting they inhabited areas with surface temperatures exceeding 50°C. The interdisciplinary approach, combining evolutionary biology, paleoclimatology, and climate modeling, provides a comprehensive understanding of plant adaptation to past climate emergencies. As Dr. Zhen Xu from Leeds' School of Earth and Environment notes, this research suggests that plants with CAM photosynthesis traits could become more dominant in a warming world. This finding has significant implications for our understanding of plant communities and their response to extreme heat and water stress. The study's insights not only contribute to our knowledge of Earth's history but also offer a glimpse into potential future scenarios, emphasizing the importance of studying plant adaptations in the context of climate change.
