Insectivorous plants sound as if they should be exotic and tropical, yet species are common in many parts of the world where there are wet peatland bogs.
There are three main groups of insectivorous plants, sundews, Venus flytraps, and the Pitcher plant. They all obtain essential nutrients, amino acids, and proteins by trapping, digesting, and absorbing small insects. However, they differ in how they trap their prey.
Their fascinating insect-trapping mechanisms ensure that they obtain nutrients unavailable from the soil in their habitats.Some of the essential nitrogen for this growth is supplied in this way, so insectivorous plants can grow in areas where conditions would otherwise have been unsuitable.
If you want to know more, please read on.
How Do Carnivorous Plants Catch Prey?
There are five main ways that carnivorous plants catch their prey.
- Pitfall trap – A hollow leaf is filled with fluid. The plants are generally slippery and deep, giving the insect little chance to escape.
- Bladder trap – The mouth of the trap is closed by a valve, and the insect activates the trigger by brusing against it.
- Flypaper trap – Sticky nectar attaches itself to the insect, trapping it.
- Snap trap – These use a quick movement to snap shut and trap their prey once they sense the insect on their trigger hairs.
- Pitcher trap – These have a long pitcher-like shape with caly sides and downward-pointing hairs to prevent the insect getting out.
Where do Insectivorous Plants Live?
Sphagnum bogs are often colonized by carnivorous plants. The round-leaved sundew grows in the tussocks of bog moss, while the smaller intermediate sundew is found on bare peat or in the drainage channels leading from raised sphagnum bogs.
This species differs from the others in having leaves held in an erect rosette, whereas the leaf rosettes of the other two are flat and pressed to the ground. The leaves of all three are paddle-shaped and covered with tiny, glistening, pin-like hairs which shine like dew in the sun, giving the plants their name.
Glands on the tip of every hair and the leaf surface produce an abundance of sticky mucilage that looks like nectar. Insects are attracted to the leaves and are soon trapped in the substance. As the insect struggles, this triggers the movement of the long, outermost hairs which wrap over the insect.
Once it is enclosed by the hairs, digestion by the enzymes in the mucilage can begin. When the liquefied remains have been absorbed, the hairs re-open, and the fly-trap is ready to start the process again.
A similar trap is set by the common butterwort, which likes the same habitat of wet rocks, marshes, fens, and peatland. It has long-stemmed violet flowers and distinctive yellow-green leaves, which form a basal rosette.
The hairs on the leaves are microscopic and much more numerous than in the sundews, with as many as 25,000 per square centimeter (160,000 per sq in). Any insect landing on the leaf is trapped by the sticky hairs, while the leaf margins roll inwards to enclose it.
A thick digestive fluid is produced by the leaf to break down the insect’s body so the plant can absorb the nutrients. Once the process is completed, the leaf reopens.
How Does The Bladderwort Trap Insects?
The circular mouth of the bladder trap is closed by a valve, and when a tiny creature brushes by, it activates the special trigger hairs that open the valve.
Negative pressure inside the trap causes water to rush in, bringing the animal in. The insect decomposes, and the remains are absorbed, with the waste products pumped out of the bladder.
The bladderworts form another small group of insectivorous plants, but their lifestyle differs from the species above. They are rootless water plants, and only the common bladderwort is abundant, growing in peatland pools.
The leaves of the bladderworts are submerged, and, as with the leaves of many aquatic plants, they are finely dissected to allow easy absorption of food for growth.
Some essential mineral salts are lacking in their environment. However, the plant obtains these essential nutrients from living tissue through microorganisms caught by its bladder traps. These are tiny, intricate traps, 1-2mm in diameter, which catch rotifers, protozoans, and small crustaceans.
Male water fleas (Daphnia) are commonly caught in traps. The males approach the traps intending to try to mate and are sucked in immediately and absorbed by the plant.
How Do Pitcher Plants Eat Insects?
There are over 100 species of pitcher plants, which can be found in Australia, Papua New Guinea, Seychelles, Madagascar, Southeast Asia, and Sri Lanka.
The leaves of the plant are shaped to form pitchers, which are partly filled with fluid. The pitchers of all these plants are brightly colored. The color, along with the sweet scent of the nectar glands at the top of the pitcher, helps to attract insects.
The insects land on the lip of the pitcher and crawl down into the depths of the water below. Once there, they cannot escape as the scaly sides and downward-pointing hairs prevent them from obtaining a grip on the pitcher.
Powerful narcotics drip into the water from the nectaries also help cause the insect’s death. The bodies are then digested by enzymes produced by special cells in the lining of the pitcher.
Are Carnivorous Plants Rare?
Carnivorous plants are considered to be a rarity in the plant world. The usual explanation for their existence is that the insectivorous habit evolved from needing protein, lacking in their acid, nitrogen-sparse habitats.
They cannot synthesize sufficient amino acids in these areas for their needs. However, Charles Darwin thought insectivorous habits were much more widespread than acknowledged today. He studied them widely, publishing a book, Insectivorous Plants, in 1875.
Despite his findings and many other studies, insectivorous plants are relatively rare compared to most other types of plants.
Plants such as the tobacco plant Nicotiana tabaccum, and potato plant solanum tuberosum are covered with hairs. Dead insects can often be seen sticking to the hairs, and enzymes capable of digesting insects have been found in the secretions from these glands.