“Feed me.” This is what the man-eating plants murmured in the 1960 horror film classic “Little Shop of Horrors” starting Jack Nicholson. OK, there are no man-eating plants, but insects, beware.
There are approximately 500 species of known insectivorous plants in the world. They mostly grow in nitrogen-poor, waterlogged soils. Like all green plants, they produce their own food by the process of photosynthesis powered by sunlight. But the insect “eating” habit evolved to give them a nutritional boost in nitrogen-poor soils.
The insect-trapping structures may resemble flowers but are really modified leaves with various mechanisms to capture an insect meal. One group is the pitcher plants which grow on the eastern coastal plains.
They have tubular leaves for capturing insects. Around the lip of the pitcher are glands that secrete nectar, which attracts insects. The upper portion of the inside of the pitcher is densely covered with stiff, downward-pointing hairs. Insects seeking more nectar can only go down into the pitcher. Below the hairs the surface is smooth and produces digestive enzymes. The hapless insect slides to the bottom of the pitcher into a pool of enzymes and bacteria where it is digested, and the resulting nutrients are absorbed by the plant.
Another group is the sundews, generally the smallest of the insectivorous plants. A few species grow in North America, but they are more common in Australia and South Africa. The leaves are small and send up as many as 200 stalked glands that secrete a sticky liquid. When an insect gets stuck and struggles to free itself, the tentacles bend over to secure it. Digestive enzymes are secreted that decompose the victim and release nutrients which the plant absorbs.
The most amazing one of all is the Venus flytrap, which was likely the inspiration for “The Little Shop of Horrors.” It is found exclusively in acid bogs of the coastal plains of North and South Carolina, and nowhere else in the world.
The plant’s insect-eating “jaws” are modified leaves arising from the ground in a swirl of up to eight jaws. The winged petiole ends with two semicircular leaf lobes united by a thick midrib. Each lobe is lined with a comb of long, stiff teeth that interlock to trap the insect.
Like the other insectivorous plants, nectar is secreted to attract the insect meal. In the middle of each lobe are three sensitive “trigger” hairs. A foraging insect must strike the hairs in an exact order to trigger the lobes to close, trapping the insect. The plant must avoid false alarm closings of its jaws to save its energy. The lobes then secrete enzymes to digest its meal.
These and other “flesh eating” plants have inspired folklore around the world. And they inspire wonder at the ingenuity of nature.
Ed Perkins farms (just vegetables) in Athens County.