Other plants, such as birches and poplars, also protect themselves by having narrower water transport cells, which makes the parts of the plant that deliver water less susceptible to blockage during freezing and thawing.
Still others die back to the ground in winter and re-sprout from their roots, or start growing as new plants from seeds when conditions are right.
To compile the plant trait data for their study, the researchers spent hundreds of hours scouring and merging multiple large plant databases containing tens of thousands of species, largely with the support of the National Evolutionary Synthesis Center in North Carolina and Macquarie University in Australia.
When they mapped their collected leaf and stem data onto their evolutionary tree for flowering plants, they found that many plants were well equipped for icy climates even before cold conditions hit.
Plants that die back to the ground in winter, for example, acquired the ability to die and come back when conditions improve long before they first experienced freezing. Similarly, species with narrow water transport cells acquired a finer circulatory system well before they confronted cold climates.
"This suggests that some other environmental pressure possibly drought caused these plants to evolve this way, and it happened to work really well for freezing tolerance too," said Zanne.
The only exceptions were plants that shed and replace their leaves seasonally these plant groups didn't gain the ability to drop their leaves during winter until after they encountered freezing, Beaulieu added.
As a next step, the researchers plan to use their evolutionary tree to find out how plants evolved to withstand o
|Contact: Kurtis Hiatt|
National Evolutionary Synthesis Center (NESCent)