New York, Dec 23

As north India, especially the hills, reels under freezing cold and dipping mercury, there are some lessons to be learnt from plants on how to cope with the cold.

Unlike animals, most plants can’t move to escape the cold or generate heat to keep them warm.

A team of researchers at the National Institute for Mathematical & Biological Synthesis, University of Tennessee, has found new clues to how plants evolved to withstand wintry weather.

The results suggest that many plants acquired characteristics that helped them thrive in colder climates -- such as dying back to the roots in winter -- long before they first encountered freezing.

To understand this, the team constructed an evolutionary tree of more than 32,000 species of flowering plants -- the largest time-scaled evolutionary tree till date.

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.

“Fossil evidence and reconstructions of past climatic conditions suggest that early flowering plants lived in warm tropical environments,” explained co-author Jeremy Beaulieu of the University of Tennessee.

“As plants spread to higher latitudes and elevations, they evolved in ways that helped them deal with cold conditions. Plants that live in the tundra, such as Arctic cinquefoil and three-toothed saxifrage, can withstand winter temperatures below minus 15 degrees Celsius,” he added.

It is not cold, but ice that troubles plants the most.

“Think about the air bubbles you see suspended in the ice cubes. If enough of these air bubbles come together as water thaws, these can block the flow of water from the roots to the leaves and kill the plant,” said co-author Amy Zanne of the George Washington University.

Some plants do have an answer to ice too. Plants such as hickories and oaks avoid freezing damage by dropping their leaves before the winter chill sets in, thus shutting off the flow of water between roots and leaves, and growing new leaves and water transport cells when warmer weather returns.

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, said the researchers.

Next on the agenda of the researchers is to find out how plants evolved to withstand other environmental stresses such as drought and heat.

The findings of the study has appeared in the journal Nature.

By:IANS