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Plants gained the ability to control water loss long ago

Ever since plants marched (metaphorically) from the sea to dry land, controlling the loss of water from leaves has been important. A key physiological feature in maintaining the balance of humidity is the stomata. Stomata are tiny holes within leaves that open and close, allowing the intake of carbon dioxide for fuel and the loss of water vapor. 

Scientists have long known stomata, at least in a basic form evolved roughly 450 million years ago, shortly after plants took to land. Still, questions about the evolution of stomata have remained, such as at what point did the plants evolve the ability to control opening and closing the stomata?

New research published in Current Biology, shows that flowering plants – evolutionary late comers – share a similar mechanism of hormone control for stomata with ferns, a much older plant lineage. 

“We’ve been able to show the same active closure mechanisms found in flowering plants are also present in ferns, a much older group of plants,” explained lead researcher Dr. Andrew Plackett of the University of Birmingham.

“Being able to better understand how these mechanisms have changed during plant evolution gives us useful tools to learn more about how they work. This will be important for helping our crops to adapt to future environmental changes.”

What this discovery means in terms of evolution is that stomata control seems to have evolved once, long ago in plants and has been retained ever since. 

“This new work confirms that the earliest plants were able to actively control the water they lost through the microscopic valve like structures on the surfaces of leaves known as stomata,” said Allistair Hetherington of the University of Bristol.

“This is important because it shows that the intracellular machinery allowing stomata to open and close was present in the earliest land plants. The research also shows that, whether stomata respond actively or passively is dictated by the environment in which the plants lived.”

Perhaps by understanding the deep evolutionary history of plants, we can see a glimpse of their future and help them better prepare for it. 

By Zach Fitzner, Staff Writer

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