Heliamphora nutans - pitcher development
In the first 3-5 years after germination Heliamphora produces tubular leaves with a slightly bent mouth. However the leaves are too narrow to catch insects of importance to nutrition. After adolescence all well-lit leaves develop pitcher shaped pitfall traps. In Heliamphora nutans the pitchers become up to 30 cm high and 3-7 cm in width at the mouth. The pitchers are closed until they reach full length. At the enlargement below the nectaries are visible as small red spots. The helmet-shaped lid is covered closely with smaller nectaries.
The closed pitchers make it possible to investigate enzyme production without contamination from outside. It has been shown that a single species Heliamphora tatai produces proteolytic enzymes. Furthermore, this species has loose wax scales on the inside of the pitcher as it is well known from Nepenthes. Heliamphora tatai thus meets all the criteria of being an advanced carnivorous plant. As young H. tatai forms a rosette at the soil surface but with time the plant gets a lignified stem lifting the 25-35 cm large pitchers up to about two meter so the plant can better compete for light against the surrounding vegetation. With time the weight of the fluid-filled pitcher may become so heavy that the stem is bend towards the ground, but it continues growth and becomes upright again, and plants with up to four meter long stems are not uncommon. The other species has creeping rhizomes.
About enzymes: Jaffe K, et al. 1992. Carnivory in the pitcher plants of the genus Heliamphora (Sarraceniaceae). – New Phytologist vol. 122 p. 733-744.
Henning S. Heide-Jørgensen, marts 2010.