How2Day: Parts of a Pitcher Plant

Pitcher plants are distinctive and deadly. Nancy Nehring/Photodisc/Getty Images
The Sarracenia, or North American pitcher plant, is a carnivorous plant. Although its principle diet is insects, it occasionally consumes spiders, mites and the odd cricket or tiny frog. The plant grows throughout the United States and Canada, but its main habitat is the southeastern coastal areas of the U.S. Pitcher plants can be grown in home terrariums and gardens by hobbyists; enthusiastic collecting has endangered the plant in the wild.

The pitcher plant is constructed specifically to make its feeding habits efficient. The business end of the pitcher plant is actually the leaves that are responsible for passive entrapment of prey. Some species have single flowers on bare stalks that are pink- to red-petaled in order to attract insects. The red flowers act as visual lures to the adjacent, nectar-laden leaves.

Pitcher plant leaves are upright hooded pitchers that look like vases. The hoods have red edges that are loaded with nectar. The pitcher chambers are distinctively colored. Most are green and have red or purple stripes, as the reddish lines signal to insects that there is nectar to be had. The most abundant nectar is produced inside the hood on a stripe running from the hood down into the chamber, and around the opening rim of the pitcher.

The rim of the tube or pitcher has good footholds for insects but the surface becomes slippery and smooth just below the rim. As the insect feeds, it loses traction and slips into the tube. The nectar contains a mild narcotic that slows the reaction time of the insect so it will eventually be unable to fly back out of the tube.

As the insect slips deeper into the pitcher, the smooth-walled section turns into a trap with downward-pointing hairs that make it easy to slide down and very difficult to go up towards the opening. The insect's struggles move it downward. The pitcher plant eventually compacts the prey into the bottom of the pitcher; it can stockpile more meals this way. The inner walls of the pitcher contain glands that secrete a digestive enzyme that breaks down the insect's body for absorption by the plant.

Another species of the pitcher plant actually collects rainwater in the pitcher that acts as an additional lure to insects. The bugs are attracted to the glinting light on the water, stay for the nectar and are tricked and trapped by the plant. The water in this species has a wetting agent that sinks and drowns the insect and, instead of a digestive enzyme, the plant allows bacteria to break down the food source so it can be absorbed.

Pitcher plants can last a long time. They spread by rhizomes that live just under the surface of the soil. Rhizomes are extremely hardy and can survive for 20 to 30 years. The root system of the pitcher plant tends to be weak. Roots are used mainly as support, since the plant feeds through passive entrapment.

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