Members of the genus Sarracenia all have modified leaves that form traps, or pitchers, used to capture insects. There is a great variety of shapes in these pitchers within the genus, however, pointing to an equally great variety of capture techniques. Most are in the shape of an upright trumpet topped with a lobe called the operculum. One of its functions is to prevent rainwater from diluting the digestive contents of the trap. Another lobe, called the keel, runs along the outside from the lip of the pitcher to its base. The single yellow, pinkish or purple five-part flower is born on a long stalk. It is quite unusual, in that it has a style in the shape of an upside-down umbrella, to ensure cross-pollination.
There are generally eight species recognized within the genus. All of them are limited to the southeastern United States, except for one that reaches as far north as the Canadian Arctic: Sarracenia purpurea, one of the showiest plants in Québec peat bogs. Its appearance is quite different from that of the other species. Its pitchers, gathered in a rosette, are curved and look more like ear trumpets than musical ones. Unlike the other species in the genus, its operculum is erect, allowing rain into the pitcher. The opening is comparatively much larger than for other pitcher plants. Its different appearance reflects the purple pitcher plant’s unusual method of capturing prey.
The outside of the trap, in addition to its role in photosynthesis, attracts prey with its bright colours and nectar secreted by the glands that cover its entire surface. The interior is divided into five zones, each with a special purpose.
- Zone 1 includes the inner surface of the operculum, with nectar-producing glands and downward-pointing hairs.
- Zone 2 is a ring about 1 cm wide, with the neck of the trap in the middle. The huge number of nectar-producing glands give this zone a shiny appearance. The surface is narrow and slippery, so insects easily lose their footing. While the boundary between zones 1 and 2 is very clear, that between zones 2 and 3 is imprecise, making for a gradual transition.
- Zone 3 occupies all the top part of the pitcher under zone 2. Its waxy surface is covered with glands that secrete a liquid containing digestive enzymes.
- The surface of zone 4, which extends almost to the bottom of the trap, lacks the cuticle that normally covers epidermal cells, so that substances are more readily absorbed through the cell wall. Long, coarse, downward-pointing hairs prevent insects from escaping.
- Zone 5, at the bottom of the pitcher, is fairly small. It has no hairs, but does have a cuticle. Its role is not well understood as yet.
Purple pitcher plant (Sarracenia purpurea)
In these plants the level of water in the pitcher (zones 4 and 5) varies with the amount of rainwater. The prey drowns in this water. Digestion relies mainly on bacterial activity in the liquid, since the enzymes secreted by the plant are too diluted to be sufficiently effective. Once insects have been digested, all that remains is the hard parts like their exoskeletons. This debris forms a mound in the bottom of the pitcher, easily visible when one tears the leaf all the way down to the base.
Sarracenia purpurea Linnaeus
The genus was dedicated by Tournefort to his colleague, Michel Sarrazin, a royal physician in Québec, who sent him a specimen in France (Barabé and Bouchard, 1977); the epithet purpurea means purple.
- Common name: Purple pitcher plant, Northern pitcher plant, sidesaddle plant
- French name: Sarracénie pourpre, petits cochons, oreille de cochon, herbe-crapaud
- Description: Rosette of trumpet-shaped leaves. Single purple flower, on a stalk about 30 to 60 cm long. Blooms in spring.
- Habitat: In Québec it is found in highly acidic peat bogs. It seems that the plant does not require an acid environment, however, since it also grows in alkaline marl fens in the Great Lakes region.
- Distribution in Québec: Widespread, even in the north
- Global distribution: Eastern North America
Reference: Barabé, D. and A. Bouchard. "Les grandes explorations botaniques des XVIIIe et XIXe siècles au Québec: 1- Avant la conquête", Bulletin de la SAJIB, vol. 3, no. 1, 1977, p. 34-40.