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Hidden life in rupestrian grasslands

Rupestrian grassland area near Serra do Cipó National Park in Minas Gerais

Rafael Soares Correa de Souza

Rupestrian fields of grass and shrubs growing in stony, nutrient-poor soil are generally found on mountaintops and plateaus. Although they represent just 0.8% of Brazilian territory, they are home to 15% of the plant species identified in the country. Ecologists and botanists have long wondered how such diversity is able to thrive in soils with such low levels of phosphorus and nitrogen. The answer seems to lie in the roots. More specifically, in the range of microorganisms (bacteria, archaea, and fungi) that colonize them. A team led by geneticist Paulo Arruda of the University of Campinas (UNICAMP), analyzed the roots of two plants commonly found in rupestrian grasslands—Vellozia epidendroides, which grows in shallow soil, and Barbacenia macrantha, which grows on rocks—and identified 522 microorganism species. The communities of microscopic beings on the roots of each plant were distinct, but certain species were found on both, mostly microorganisms that specialize in transporting phosphorus and converting the insoluble form of the mineral into the soluble form, which is then absorbed by the plants, or those capable of recycling nitrogen (The ISME Journal, December 20, 2022). “We showed that microorganisms play an essential role in helping plants adapt to the extreme conditions of this environment,” says geneticist Rafael Souza, one of the authors of the study.