SAN FRANCISCO, Jan. 15 (Xinhua) -- U.S. biologists have found that the flowering plant's dominance on our planet is mainly due to the "genome downsizing" occurring more than a hundred million years ago.
Before the appearance of angiosperms, or flowering plants, the Earth was dominated by ferns and conifers. Then, flowering plants appeared about 150 million years ago during the early Cretaceous and rose to dominance in most terrestrial ecosystems.
The reasons behind flowering plants' rapid spread and diversification has long been debated among biologists.
Prevailing hypotheses have suggested that angiosperms rose to dominance through an increase in their photosynthesis ability and carbon gain, but they failed to explain the reason behind such changes, according to the study published Thursday in the journal PLOS Biology.
"We now provide strong evidence that the success and rapid spread of flowering plants around the world was the result of genome downsizing," said Kevin Simonin from San Francisco State University and Adam Roddy from Yale University, authors of the study.
Genome size is the total amount of DNA contained within one copy of a single genome.
"Smaller genomes permit the construction of smaller cells that allow for greater CO2 uptake and photosynthetic carbon gain," said the authors.
In other words, smaller cells would allow flowering plants to pack more veins and pores into their leaves, which facilitate their intake of carbon dioxide from the air and better water distribution.
As a result, flowering plants could maximize their productivity through photosynthesis, gaining a competitive edge over other plants.
"Genome downsizing occurred only among the angiosperms, and we propose that it was a necessary prerequisite for rapid growth rates among land plants," they said.
"The flowering plants are the most important group of plants on Earth and now we finally know why they have been so successful," they added.