Scientists have found an explanation for how flowering plants became dominant so rapidly in ecosystems across the world - a problem that Charles Darwin called an 'abominable mystery'. Researchers from San Francisco State University and Yale University in the US found that flowering plants have small cells relative to other major plant groups and that this small cell size is made possible by a greatly reduced genome size. "The flowering plants are the most important group of plants on Earth, and now we finally know why they have been so successful," the researchers said. For more than 200 years, scientists have speculated about the incredible diversity and success of flowering plants, which form the basis of our food system and are responsible for fuelling much of the animal diversity we see today. Over the last thirty years, researchers have shown that the flowering plants have unparallelled rates of photosynthesis. This has allowed them to grow faster and to outcompete ferns and conifers which had dominated ecosystems for hundreds of millions of years, researchers said. The secret to the metabolic success of flowering plants is their specialised leaves that facilitate faster rates of water transport and carbon dioxide uptake. However, how the flowering plants were able to build leaves capable of these high rates of transpiration and photosynthesis has remained a mystery. In a study published in the journal PLOS Biology, the researchers argue that these anatomical innovations are directly linked to the size of their genome. Because each cell has to contain a copy of the plant's genome, smaller genomes allow cells to be smaller, researchers said. If cells are smaller then more cells - such as those specialised for photosynthetic metabolism and water and nutrient transport - can be packed into a given volume of space, they said. By shrinking the size of each cell, water and nutrient delivery can be made more efficient. Comparing hundreds of species, the researchers found that genome downsizing began about 140 million years ago and coincided with the spread of the earliest flowering plants around the world.
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