Why do insectivorous plants eat insects

Aha : Why do some plants eat meat?

Mosquitoes and spiders get caught in the tentacles of the sundew or drown in the pit of a tropical pitcher plant. Broken down by digestive juices, all that remains of the small animal is a framework made of chitin.

The leaves of some carnivorous plants are cemeteries from the empty shells of insects. It is hardly possible for such plants to live without meat. Because the soil on which they grow often doesn't even provide the bare essentials: nitrogen.

"All plants depend on nitrogen," says Peter Dittrich, emeritus botanist at the Ludwig Maximilians University in Munich. The air contains around 78 percent nitrogen. Plants cannot break the bonds of nitrogen atoms. Only special bacteria and algae can do this. "In order to build proteins, plants have to take up nitrogen through their roots."

Carnivorous plants, however, live on low-nitrogen soils, such as bogs. To make ends meet here, you need nutritional supplements. The Venus flytrap would also be satisfied with pieces of cheese. Since nobody feeds her with it, she has specialized in catching small animals.

The range of catching mechanisms is fascinating. The leaves of the dwarf jug, coated with smooth wax, are a slide for articulated animals. The water hose, on the other hand, uses a suction trap and pulls the prey down under water with negative pressure. The hook-leaf liana is different: it changes its leaf dress depending on the nutrient situation. In good times she puts on ordinary leaves. "In contrast, when there is a lack of nitrogen, it forms sticky leaves to catch insects," says Dittrich. The hook leaf is a "die-hard vegetarian". Thomas de Padova

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