No plants evoke as much interest as carnivorous plants that trap and consume live animals. But why are there plants that have evolved this rather unusual (for a plant) trait?
Typically, plants obtain minerals and essential elements through their roots from the soil they are growing in. But, carnivorous plants get their minerals from catching live prey, this is because they have evolved to live in extremely nutrient-poor soils. In fact, give a carnivorous plant a rich, ‘healthy’ soil and you’ll most likely kill it!
Several methods for catching prey (usually insects) have evolved, which can be seen in some of the most well-known carnivorous plants below.
Dionaea muscipula – Venus Fly Trap
The most famous and easily recognisable carnivorous plant is the Venus Fly Trap. Dionaea is a monotypic genus meaning it contains only one species (D. muscipula). The trap mechanism of the Venus Fly Trap is unique in the plant kingdom. 3 small trigger hairs inside the trap need to be touched twice in 20 seconds to activate the trap (making the Venus Fly Trap the only plant that can count!) and snap it shut on the unsuspecting prey. As the prey struggles, the trap seals tighter until escape is impossible and the prey can be slowly digested.
Sarracenia spp. – North American Pitcher Plants
There are several species of Sarracenia with many subspecies, varieties, forms and hybrids. All of which trap their prey inside modified leaves called pitchers. These pitchers can take the form of long trumpet-like traps or low-lying bulbous traps. Prey is lured to the top of the trap by a sweet ‘nectar’ secreted by the plant. Directly below this lure, the pitcher is extremely slippery which can cause insects to suddenly lose their footing and fall into the trap. Fine downward-pointing hairs prevent the hapless prey from climbing back out. They are digested within the pitcher.
Drosera spp. – Sundews
There are around 200 species of sundew making them the most diverse genus of carnivorous plant. They catch prey by using sticky droplets of ‘dew’ on their leaves. As they struggle to escape the sticky leaves, insects usually get caught by more dew making it even harder to get away. Eventually, the prey can fight no more and become a meal as the drosera digests them.
Nepenthes spp. – Monkey Cups
Nepenthes are vining carnivorous plants with cup-like extensions at the end of their leaves. The cups contain water and digestive enzymes to drown and digest prey that falls in. Prey are attracted by a nectar-like substance above the cup but then slip into the trap. Often, downwards pointing teeth’ prevent escape!
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