The interaction between plants and atmosphere forms the basis of the carbon cycle and is amongst the most important processes for maintaining life on the planet today. Photosynthesis removes carbon dioxide from the atmosphere and in return forms the base of the food chain and produces the oxygen we, as animals, need to breathe. Equally, the composition of the atmosphere influences the climate and thus the availability of resources, governing where plants are able to survive. The relationship between the two can be committed to the fossil record by such physical proxies as the number of stomata in leaves and by the palaeolattitude of different species. Other chemical proxies, such as isotopic ratios, can also help elucidate what the atmosphere was like at the time a plant was preserved. Similarly, atmospheric proxies can also be used to make inferences about past plant life in the absence of fossil remains. Joining us to discuss the link between plants and atmosphere is Prof. Jennifer McElwain of Trinity College Dublin, Ireland.