Life on earth would have been impossible without the humble fungi, as they played an essential role in the creation of an oxygen-rich atmosphere, claims a study.The study showed that fungi played a critical part in establishing a breathable atmosphere on Earth by "mining" the nutrient phosphorus from rocks and transferring it to plants to power photosynthesis.The amount of phosphorus transferred could have been very large under the ancient atmospheric conditions, but fungi had the power to dramatically alter the ancient atmosphere, the researchers said."The results on fungal interactions present a significant advance in our understanding of the Earth's early development. Our work clearly shows the importance of fungi in the creation of an oxygenated atmosphere," said Benjamin Mills from the School of Earth and Environment, at the University of Leeds."The nature of the relationship between fungi and plants could have transformed the atmospheric carbon dioxide, oxygen and ultimately global climate in very different ways, depending on the type of fungi present," added Sarah Batterman, from the varsity's School of Geography.For the study, detailed in the journal Philosophical Transactions B, the team used a computer model to carry out experiments where plants and fungi were grown in atmosphere resembling the ancient Earth -- during which plants did not have roots and were non-vascular, meaning they could not hold water or move it around their system.Fungi helped the plants to extract minerals from the rocks to aid their growth. The fungi in return received the carbon which the plants produced as they photosynthesised carbon dioxide from the atmosphere."We found the effect was potentially dramatic, with the differences in plant-fungal carbon-for-nutrient exchange greatly altering Earth's climate through plant-powered drawdown of CO2 for photosynthesis, substantially changing the timing of the rise of oxygen in the atmosphere," said Katie Field from the varsity's Centre for Plant Sciences.