3 minute read
Carnivorous plants
Charles Darwin was one of the first scientists to discover that some plants are carnivorous; an idea that seemed completely ridiculous - animals eat plants, not the other way around!
In the natural world animals and plants adapt to the environment in the most ingenious ways. Carnivorous plants grow in nutrient poor soils and since they are rooted to the ground in one place, they have evolved strategies to attract and trap insects and then extract nutrients from their bodies. Australia is a hotspot for carnivorous plants and with nearly 250 different species of sundew, pitcher plants and bladderworts, we have more species of carnivorous plants than any other continent. Many readers may be surprised to learn that the Climbing Pitcher Plant, Nepenthes mirabilis, grows on the coastal lowlands near Eubenangee Swamp and Bramston Beach. There is also an endemic species of sundew, Drosera schizandra, in wet, shady areas near the summit of Mount Bartle Frere. Sundews (genus Drosera), the most widespread carnivorous plant in North Queensland, are easily overlooked as most are small, round and about the size of a fifty-cent coin. They grow in sandy soils and in moist places where seepage occurs, such as creekbanks, edges of swamps or around rocks. The leaves and stems are covered with sticky glands designed to trap small insects and the unfortunate victims are rarely able to free themselves. Sundews can also move their stems to enclose their victims in the process of capture. The glands contain digestive enzymes that dissolve most of the insect to a nutritious liquid leaving only the exoskeleton on the plant. Several Sundew species have a different form and grow tall stems similar to the Rainbow Plant. Pitcher plants use pitfall traps to capture insects. The ‘pitcher’ is an extension and modification of the leaf and is designed to hold liquid. Insects are attracted to the ‘pitcher’ by bright colours and patterns or nectar and fall into the trap. Once in the trap, insects are prevented from escaping as the ‘pitcher’ is designed with slippery walls and small trap hairs at the mouth. The exhausted victim eventually drops into the liquid and drowns before being dissolved by digestive enzymes. The lid on the ‘pitcher’ most likely functions to keep rain from diluting the liquid. Pitcher plants in North Queensland belong to the genus Nepenthes with several species still not fully described by botanists. Bladderworts are carnivorous plants with flowers that look like small orchids. They have no leaves and rely on nutrients from the small invertebrates (eg mosquito larvae) they catch via trapdoors on underwater stems. Some species are found in wet sand or mud where they capture small microscopic animals such as rotifers. All bladderworts belong to one genus, Utricularia, and there are 18 different species in this genus in North Queensland. Another genus of carnivorous plant is the Rainbow Plant, Byblis liniflora. Its stems are covered in sticky glands which trap insects. The Rainbow Plant is similar in structure to some species of Sundew but cannot move its stems and therefore acts like a form of flypaper trap. Although flowers on many carnivorous plants are capable of self-pollination, they also rely on insects for pollination services. To prevent the insect pollinators being accidentally devoured, sundews and pitcher plants have their flowers on long stalks away from the deadly traps below. The flowers are often coloured pink, mauve or yellow to attract insect pollinators. All carnivorous plants in Queensland are protected under the Nature Conservation Act 1992,
Sticky glands on the stem of Rainbow Plant, Byblis liniflora
Insects trapped in Sundew Drosera spp
Pitcher Plant Nepenthes spp.
Flowers of Rainbow Plant Byblis liniflora A rosette form of sundew, Woolly Sundew, Drosera lanata
