Since the nineteenth century, botanists know that the leaves have “pores”, called stomata, which contain an intricate internal network of air channels. But until now it was not understood how those channels formed in the right places to provide a constant flow of carbon dioxide (CO2) to each plant cell.
A new study, led by Andrew Fleming and Marjorie Lundgren, and published in Nature Communications, used genetic manipulation techniques to reveal that the more stomata a leaf has, the more air space is formed. In this sense, the channels act like bronchioles, the tiny passages that carry air to the exchange surfaces of human and animal lungs.
The authors demonstrated that the movement of CO2 through the pores probably determines the shape and scale of the network of air channels. The discovery marks a breakthrough in our understanding of the internal structure of a leaf, and how tissue function can influence the way they develop, which could have ramifications beyond plant biology, in fields such as evolutionary biology and in agriculture.
“So far,” explains Fleming in a statement, “the way in which plants form their intricate patterns of air channels has been surprisingly mysterious to experts. This great discovery shows that the movement of air through the leaves configures its internal functioning, which has implications for the way we think about evolution in plants. The fact that humans have inadvertently influenced the way plants breathe, by growing wheat that uses less water, suggests that we could point to these networks of air channels to develop crops that can survive the most extreme droughts, an effect of climate change.”
According to Lundgren, “scientists have long suspected that the development of stomata and the development of airspaces within a leaf are coordinated. However, we weren’t quite sure what drove who. It was like one. Which came first, the chicken or the egg? Using a set of experiments with X-ray image analysis, our team answered these questions using species with very different leaf structures. While we show that the development of stomata begins the expansion of airspaces, we go one step further to show that stomata actually need to exchange gases for airspaces to expand. This represents a much more interesting story.”
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