The Predatory Character Of Insectivorous Plants – Drosera (The Sundew)
Insectivorous plants have come to be very prominent in biological studies owing by the unique way it obtains nutrition from animals and from the bodies of insects and other smaller animals. This method of obtaining food is in addition to the normal photosynthetic process since the insectivorous plants possess chlorophyll. The mechanisms by which the prey is captured and subsequently treated show some variation and are among the most fascinating of all plant adaptations. All the species are included in a small number of flowering plant families and few representative genera such as Drosera would be described below.
Drosera: The Sundew
How Drosera Species Engulfs and Digests its Prey: The Drosera is a genus of the family Droseraceae with three British species, namely, Drosera rotundifolia, Drosera anglica and Drosera intermedia(Drosera longifolia). All are inhabitants of damp, peatylocalities. The plant has a rosette habitat and each leaf forms an organ by which the insect is trapped and digested. Its upper surface bears a number of multicellular glandular hairs or tentacles which are long at the leaf margins and shorter in the center. The whole leaf surface is always sticky due to secretary activity of other smaller glands and the knob-like glandular ends of the tentacles secrete proteolytic enzymes capable of digesting the animal body. The same glands function also to absorb the decomposition products.
The reaction of the leaf on being stimulated by the presence of an insect is to bring about curvature of all the outer tentacles inwards towards the leaf centre, so that the insect is completely enmeshed. All the glands then vigorously secrete to form a large drop of fluid in which the animal is submerged. Charles Darwin showed that the curvature is partly chemonastic since it can be induced by liquid substances which contain nitrogenous material, but comparatively few others. However, response to contact is also observed and similar results are obtained when a whole variety of solids are touched against the tentacles. The movements are growth curvatures of the tentacles and are caused by increased growth rate of a tentacle, causing bending towards the leaf center. The stimulus can be transmitted through the leaf, since if only one tentacle in the center of the leaf is stimulated; the more distantly-situated tentacles curve inwards. It is probable that the conduction of the excitation is hormonal and that an auxin is involved.
Insectivorous plants, also known as carnivorous plants, have evolved unique adaptations to obtain essential nutrients by capturing and digesting insects. These plants have developed predatory characteristics to thrive in nutrient-poor environments.
Types of Insectivorous Plants
1. Pitcher Plants (Nepenthes): These plants have modified leaves that form a deep, slippery cup to trap insects.
2. Sundews (Drosera): Sundews have leaves covered in sticky droplets of glue-like substance that trap insects.
3. Venus Flytraps (Dionaea): These plants have modified leaves that can snap shut quickly to capture insects.
4. Bladderworts (Utricularia): Bladderworts have bladder-like traps that suck in insects.
Predatory Characteristics
1. Trapping Mechanisms: Insectivorous plants have evolved various trapping mechanisms, such as sticky surfaces, slippery cups, or snap traps.
2. Attractants: These plants often produce attractants, like nectar or fragrances, to lure insects into their traps.
3. Digestive Enzymes: Insectivorous plants produce digestive enzymes to break down the insect’s soft tissues and absorb the resulting nutrient-rich soup.
4. Nutrient Uptake: These plants have adapted to absorb nutrients from the digested insects, often through specialized roots or leaves.
Adaptations for Predation
1. Modified Leaves: Insectivorous plants have modified leaves that form traps, produce sticky substances, or have other specialized features.
2. Sticky Substances: Many insectivorous plants produce sticky substances, like glue or resin, to trap insects.
3. Trigger Mechanisms: Some plants, like the Venus flytrap, have trigger mechanisms that respond to insect movement or touch.
4. Digestive Cavities: Insectivorous plants often have digestive cavities or bladders that contain digestive enzymes and absorb nutrients.
Ecological Role
1. Nutrient Cycling: Insectivorous plants play a crucial role in nutrient cycling, obtaining essential nutrients from insects in nutrient-poor environments.
2. Food Source: These plants provide a unique food source for certain insects, like spiders and ants, that have adapted to feed on the trapped insects.
3. Ecosystem Engineering: Insectivorous plants can modify their environment through their trapping mechanisms, creating a unique microhabitat for other organisms.
In summary, insectivorous plants have evolved remarkable predatory characteristics to obtain essential nutrients in nutrient-poor environments. Their unique adaptations, such as trapping mechanisms, attractants, and digestive enzymes, enable them to capture and digest insects, playing a crucial role in nutrient cycling and ecosystem engineering.
