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A new research suggests that plants may have ‘crawled’ from the sea earlier than it was previously thought.
All plants evolved from green algae, scientists say. Previous assumptions stated that the algae developed life cycles with alternating stages, before they adapted to terrestrial life.
The new research – published December 16 in the journal Trends in Plant Science – suggests otherwise.
According to Jesper Harholt, co-author of the paper and an Associate Professor in the Department of Plant Glycobiology at Carlsberg Laboratory in Copenhagen, the researchers had to find simpler model organisms by going backwards in evolution.
Botanical researchers stated in the 1980s that land plants descended from algae that had already adapted to terrestrial life. However, no one was able to provide evidence in support of that model until now.
For their research, Dr. Harholt and his colleagues looked at freshwater algae species, and saw that some of them had complex cell walls. Because the buoyancy of the water counteracts gravity, water plants usually have less complex cell walls.
However in land plants, the cell wall is crucial for structural support. If it weren’t for the cell walls, the plants would be weighed down due to gravity, the researchers said.
Researchers suggested that the algae that were most similar from a genetic point of view to terrestrial plants were the secondarily aquatic algae. Both terrestrial plants and these algae must have had a common ancestor that lived on land for a long time (hundreds of millions of years) before it finally developed alternating life-cycles.
Peter Ulvskov, co-author of the study and a professor of plant science at the University of Copenhagen, said that ‘secondarily aquatic’ refers to organisms that used to be terrestrial but then adapted to an aquatic life style.
Unfortunately, researchers will not be able to find fossil evidence, because the difference between terrestrial and aquatic algae is normally not preserved in fossils, according to Harholt.
Study co-author Øjvind Moestrup, an evolutionary biologist and algae expert at the University of Copenhagen, sated that aquatic green algae were long thought to be direct ancestors of land plants.
Many questions remain unanswered, and researchers expect some scepticism from others in the field since currently they only have genetic and structural data to go on.
Image Source: iflscience
