When nutrients sufficient for survival cannot be found in native environments, evolution solves the problem with carnivorous plants. Bladderworts, known by their scientific name Utricularia, for example, use small bladders to trap and digest aquatic animals.
Conventional theory holds that the bladders on the roots of Utricularia are triggered by the motion of aquatic critters on sensitive hairs. When triggered, the bladder sucks in a gush of water, capturing the prey and other materials in the water.
Scientists have long thought that the large amount of algae, pollen, moss, fungi, and other material caught in the bladderwort's sacs represents mere by-catch, accidentally caught in the process of looking for a real meal. But in a new study published in the Annals of Botany, researchers at the University of Vienna find that bladderwort benefits from much of it's vegetarian buffet.
Scientists evaluated the actual catch across a range of bladderwort species. They found that little aquatic animals made up only about 10% of the contents of the bladders, while algae constituted fully 50% of the catch. They evaluated the plants' diets and correlated them with the growth and health of the plants. The conclusion? Bladderworts use nutrients in the algae and pollens they trap, but don't benefit from mosses, fungi, and mineral particles sucked into the bladders.
Even more groundbreaking, the scientists found that the bladder traps can fire autonomously, independently of the proximity of prey. This means that the plants can survive on a vegetarian diets for periods when prey is scarce.
The carnivorous bladderwort still needs prey animals to get sufficient nitrogen, which is generally lacking in the environments in which the bladderwort thrives. But even in environments rich in aquatic animals, the bladderwort consuming a goodly portion of algae and pollen thrived better than peers eating a more protein-based diet. So it seems that even carnivorous plants can benefit from meatless Mondays.