The meat eating plants in Sweden are so possessive on nitrogen pollution that they are able to eat fewer bugs. It may not be a good thing for the plants, a new study by Jonathan Millet, a plant ecologist at Loughborough University in U.K.
Nitrogen is an essential nutrient for all plants. But, like other carnivores species in plant and animal kingdom in the universe, the round leaf sundew plant scientifically named as Drosera rotundifolia has evolved to live in nitrogen-poor environments by supplementing its diet with insects.
Throughout the world where there is a rapid growth of industries, the industrial activities have caused an increase in nitrogen pollution, so that more of the element is seeping into soils along with rainfall.
In Sweden, where the experiments took place, the southern and central parts of the country are more polluted than the north, which has less industry.
Accordingly, the team found that round leaf sundew plants in southern Swedish bogs are taking up more nitrogen via their roots than those in northern and central bogs, said study leader Millet, a plant ecologist said.
"They're more full-up," Millett said. "If you've got enough food in the fridge, you don't go to the shops to buy some more." the biologist added.
For the work, the team accumulated tissue samples from this autotrophic entities and its insect prey, mostly small flies called midges from three bogs.The scientists also sampled sphagnum moss, to serve as a control plant that receives all of its nitrogen via its roots and none from insects.
Bogs are "not the most pleasant environments to work in," Millett added. "It's impossible to stay dry—no matter how hard you try, you end up with willies full of water."
Once their fieldwork was done, the team ground up the samples and research the kind of nitrogen contained in each. The nitrogen atoms drawn in by plants are slightly lighter than the ones in bugs, because biological processes tend to favor the heavier version of the element.
It therefore looks for chemical tracers to pinpoint whether most of the nitrogen in a sample came from insects or from the soil.
From the data, the team figured out that sundew plants in polluted areas were getting more nitrogen from soil, implying that the predatory plants are laying off bugs.
It's "what people would predict, but no one has measured it before," said Millett, whose study appears in the July issue of the journal the “New Phytologist”.
All in a view, nitrogen pollution has become a global problem that has "large and real" impacts on ecosystems, Millett noted.
Now carnivorous plants are in great risk, which have evolved to live only in low-nitrogen environments.
It might seem like a boon to have lots more nitrogen handy, the plants' predatory trappings, such as specially shaped, sticky leaves suck up a lot of energy. This makes the plants weaker and less able to compete with hardier, faster growing plants that will take advantage of higher nitrogen levels.
For instance, Millett suspects that "heather and grasses will start to 'take over' and shade the carnivorous plants, which don't grow too well in more shaded environments.
"The carnivorous plants do tend to do better on an individual basis when there is more nitrogen, but this ... isn't enough to keep up with these more competitive plants."he commented.
Aaron Ellison, a Harvard University ecologist, said in an email that the new, "carefully done field study" fits with "other studies of this phenomenon done with other species of carnivorous plants."
Because the roundleaf sundew is so widespread, it's not in danger of going extinct, study leader Millett added. But rarer carnivorous plant species that are hanging on in small populations could be in trouble.
"I would be surprised if nitrogen pollution doesn't have an impact on carnivorous plants" as a group, he said.