Discovery of an upside down, carnivorous plant in Brazil

I've always been a fan of carnivorous plants.  Pitcher plants, Venus flytraps... very cool.  An article just published in PNAS describes a very bizarre plant that has been recently characterized as carnivorous.  The flowering plant, from the genus Philcoxia, is a pathetic specimen.  Found in dry savannas of the cerrado in central Brazil, the stems are leafless, which means it resembles many of my potted plants here at the house.

It turns out that the leaves of Philcoxia are actually underground! Most plants would find this adaptation ridiculous.  The primary function of a leaf is to capture sunlight and produce energy through photosynthesis.  What kind of freakish plant would put the leaf underground where there is no light?  A murderous plant, of course.

What Pereira et al. show in the PNAS paper (abstract) is that the leaves of Philcoxia have evolved to trap and eat nematodes in the soil.  The data to support this comes from an elegant study using nematodes that had been fed nitrogen-15 (15N), an isotope of natural nitrogen.  Releasing the nematodes in the vicinity of the plant, they measured the change in 15N in the leaves after two days.  They show that the absorbed 15N increases from nearly undetectable levels before the experiment to about 15% of all nitrogen content by Day 2.  They talk in the methods about how they extensively washed and dried the leaves to remove all traces of 'nematode remains', but the greatest risk in this experiment is that the 15N they are measuring is simply from the residue of dead worms on the leaves.  Nevertheless, they also show that the leaves are covered  with a sticky sap and that enzymes on the surface are available to break down the corpse for consumption, as found in other carnivorous plants. Interestingly, the glands that produce the sap are also similar to those found on other carnivorous plants.  So, it certainly seems plausible that another plant has found its way to the dark side.  Better call NCIS (that's Nematode Criminal Investigative Service).

Maybe I'll just start telling people that the dead plants I have around my house are rare Philcoxia from central Brazil and that they are supposed to look dead.  Maybe I'll tell them that I have re-engineered them to eat, um, larger prey. I wonder if carnivory could be engineered into grass?  That would keep the neighbor's dog off of the yard!! Ahh, the possibilities...