Why would any plant want to bury its leaves underground? We all know that leaves are used for photosynthesis, so surely the idea makes no sense.
That's why Professor of Botany Rafael Oliviera was so intrigued when a colleague returned from a field trip and described a plant with adapatations of a very peculiar kind.
"I had never seen a plant with underground leaves before," he said. "It doesn't make a lot of sense to have leaves underground because there is less sunlight -- so we hypothesized they're getting some other kind of benefit from the leaves."
Philcoxia minensis lives in sandy soils of the Cerrado, a tropical savannah region in Brazil and one of the world's 34 'biodiversity hotspots'. Philcoxia has both 'normal' leaves on stems above ground, and a network of minature leaves, each no larger than a pinhead, underground.
It's not that the underground leaves get no sunlight at all. In fact, they can capture sunlight through the white, sandy soil. However, that's not their only function.
These underground leaves secrete a sticky substance that traps nematodes, miniscule worms in the sandy soil. To test if the plant was truly digesting the worms, the scientists fed the plants nematodes marked with an uncommon isotope of nitrogen. When they tested the plant's leaves, they found the same isotope present, confirming that the plant was indeed using enzymes to digest the worms.
This is the first time that a plant has been found which uses underground leaves to trap prey, and the first plant that has been found to digest nematodes, a common strategy in fungi.
"It's a great example of how plants, which can't move to find food and
water, are able to develop interesting mechanisms to deal [with] extreme
environments," says Rafael Oliviera
It's also a reminder of how important the Brazilian Cerrado is for conservation - but it's being destroyed at faster than the Amazon rainforests, largely to grow soy and for cattle ranching.
Find out more about the Brazilian Cerrado in this video by the Royal Botanic Garden Edinburgh and the WWF.
Find out more about Philcoxia minensis at Inside Science.