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Plant Adaptations II
Below is a pictorial review of carnivorous plants seen in lab. |
Carnivory
Swampy soils are often nutrient poor because the constantly wet conditions wash nutrients from the soil. Plants in these areas face the challenge of obtaining enough nitrogen. All plants need nitrogen, and it is a key component in commercial fertilize. Nitrogen is used in building proteins (such as enzymes), nucleic acids (like DNA), and in the pigment chlorophyll, which plants use for photosynthesis. Insects contain lots of protein and nucleic acids, and so provide a good source of nitrogen to whichever plants can catch them. Thus, plants catch insects not to get food, but to get extra nutrients. Think of insects as vitamin pills for carnivorous plants.
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Pitcher Plants
The entire leaf of the pitcher plant is modified to hold rain water. It has a tube-like base and a flared top. The plant may lure insects in to investigate with bright colors or interesting fragrances that make the pitcher resemble a flower. Once inside, it is difficult for the insect to fly up and out of the narrow pitcher. The walls of the pitcher are smooth, slippery, and sometimes covered with backward pointing hairs. This prevents the insect from crawling out. When the insect tires, it falls into the water at the base of the pitcher, drowns, and decomposes. The plant then absorbs the nitrogen released into the water.
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Venus Flytraps
Venus flytraps use a different strategy for catching insects. The tip of the leaf is modified into a trap. When a curious fly brushes against several of the trigger hairs hidden inside the trap, the trap snaps shut, digestive enzymes are secreted, and the hapless insect is slowly dissolved. The leaf then absorbs the nitrogen from the remains.
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Venus Flytrap |
Pitcher Plant |
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