A new theory of plant evolution suggests that the 400 million-year drive of flora across the globe may not have been propelled by the above-ground traits we can see easily, but by underground adaptations that allowed plants to become more efficient and independent.
As plant species spread north and south from their nutrient-rich tropical beginnings, the fine tips of their roots became narrower and more widespread to help them explore increasingly poor soil for vital nutrients, according to a study in the journal Nature led by researchers from Princeton and the Chinese Academy of Sciences (CAS) in Beijing.
In addition, as plants spread into unpredictable environments such as arid deserts they grew less dependent on the symbiotic fungi that colonize roots and help host plants obtain the essential plant nutrients nitrogen and phosphorous.
The findings reconsider how plants adapted to new environments as they evolved. Scientists have in the past focused on above-ground characteristics, primarily leaf traits and the efficiency with which plants absorb sunlight for photosynthesis.
Instead, the study authors found for the first time that root diameter and reliance on fungi — or the lack thereof — are the traits that most consistently characterize the plant community across entire biomes, which are large distinct communities of animals and plants such as a desert, temperate forest or savanna.