Whilst walking through the beautiful heathland of the New Forest, to my surprise I chanced upon a very small, brilliant-red, round-leaved plant growing close to the ground. If I hadn’t been trying (and failing) to chase a grasshopper and take its picture, I probably wouldn’t have noticed it. On closer inspection, the leaves possessed curious hair-like structures, tipped with a glistening, sticky substance. As beautiful as it looked sparkling in the sun, I realised it must be a carnivorous plant, after spotting an unfortunate partially-digested insect stuck to one of its leaf stalks. I found out that this species is a round-leaved sundew.
— Kate Dey (@KateDey1) August 17, 2014
I’ve always been intrigued by the fantastic carnivorous plants you see eating rats and the like on the telly, but had never really considered the smaller yet intriguing species found in Britain. It turns out that there are at least 13 species of carnivorous plants native to the British Isles, originating from three genera: Drosera (sundews), Pinguicula (butterworts) and Urticularia (bladderworts). These plants grow in wet habitats, such as bogs, fenland and wet heathland, which are nutrient poor places. This second habitat characteristic is why they digest small organisms as a primary source of nutrition. If there are very few nutrients in the soil there is no point in them having substantial root systems. Therefore, carnivorous plants often have thin, underdeveloped roots or no roots at all.
Sundews are found throughout Britain and have round or oblong leaves, arranged in the shape of a rosette from the base if the plant. These leaves possess red stalks, tipped with glandular heads which produce a sweet, sticky substance called mucilage. Some insects are attracted to this substance since it looks like water. When an unsuspecting insect touches the mucilage it gets stuck – the more it struggles the more covered in the substance it becomes, until it suffocates. The movement of the insect generates action potentials (a change in electrical potential) within the plant’s cells, which travel from the stalk to the leaf surface. These cause the hair and leaf to curl, and as more stalks bend inwards the insect gets more and more trapped. Digestive enzymes are released from the glandular heads and the plant absorbs the nutrients.
See a video of a sundew trapping its prey.
Sundews and butterworts trap insects in a similar way. Butterworts possess a rosette of flat leaves in the summer (larger than that of the sundew and often forming the shape of a star) and are covered in sticky mucilage producing glands. Many of these glands are on stalks, but these tend to be shorter than the sundew’s. The insects become stuck in the mucilage (triggering the production of more mucilage) and are then digested. Some species can bend the edges of their leaves in slightly, bringing the insect into contact with more glands. Roots of butterworts are thin and white – they are simply there to anchor the plant and absorb water. In temperate species, the roots wither away in the winter when the winter-resting bud is produced (the hibernaculum) and the plant enters a dormant state to conserve vital nutrients.
Bladderworts are different from both sundews and butterworts. First of all, they tend to be aquatic. They are rootless and thread-like, with branches of stolons (specialised roots or stems) on which grow fine photosynthetic leaves. Bladderworts possess small, bladder-like traps and thrive in still and open pools, ponds and ditches. The traps work by using a vacuum-driven mechanism. Glands on the inner surface of the trap absorb water, and so create a partial vacuum within. Sealing the vacuum is a ‘door’ that is fringed with sensitive bristles. If a small water creature touches one of these bristles, it acts as a lever, opening the door, breaking the seal, and causing water to rush into the trap along with the creature. The door seals behind it before digestive enzymes are secreted into the trap. Bladderworts are one of the fastest know killers of the animal kingdom – their traps can suck in a mosquito larvae in 1/50 of a second!
See a video of a bladderwort trapping its prey.
Britain may not be a tropical paradise with the huge, extravagant plants that you would expect to find in a rainforest, but look a little closer and you will find a miniature world that is just as interesting.
Beatty. R, Bright. D, Green. J, Kinchen. J, MacDonald, R, Rohr. S, (2001), Aquatic Life of the World, p.82 to 83, Marshall Cavendish Corporation
National Geographic, (2014), Meat-eating plants, [online], available at http://kids.nationalgeographic.com/content/kids/en_US/explore/science/meat-eating-plants/ accessed 15 August 2014.
Royal Botanic Gardens, Kew, (2014), Dorsophila rotundifolia, [online], available at: http://www.kew.org/support-kew/adopt-a-seed/drosera-rotundifolia.htm accessed 15 August 2014
Wildlife Trusts, round-leaved sundew, (2014), [online], available at: www.wildlifetrusts.org/species/round-leaved-sundew accessed 15 August 2014.
Wildlife Trusts, butterwort, (2014), available at: http://www.wildlifetrusts.org/species/butterwort accessed 17 August 2014
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