Symbionts in the Traps of Carnivorous Pitcher Plants: Who Needs Whom?
Hochschuljubiläumsfonds; W. Adlassnig and M Peroutka (2006-2007)

In carnivorous pitcher plants, prey is caught in cone shaped leaves, filled with digestive fluid. Trapped animals die of drowning, their tissues are dissolved and their nutrients are absorbed by the plant. This type of carnivory can be found in 121 species from five families. The traps however do not serve only for killing; they also host complex communities of bacteria, fungi, protozoa, algae and higher animals. Young traps of pitcher plants are usually almost sterile but within a short time period they are colonised by immigrating organisms.<br /><br />In this study, we will monitor the process of immigration under controlled conditions using a wide range of microbiological, physiological and microscopic techniques. We will focus on the issue, if these immigrants are useful for the plants, if they take part in the digestion of animal prey and if mutualistic or predatory relationships are formed within the trap community. Furthermore, we will examine if the pattern of immigration depends on the plant species or on the environment of the plant.<br /><br />Based on a series of preparing experiments, we predict the existence of two functional groups of pitcher plants. The first one produces an aggressive pitcher fluid dissolving the prey autonomously. Only few organisms are able to survive in this uncomfortable and stressful environment. The less aggressive pitcher fluid of the second group permits the survival of a great number of aquatic organisms. These organisms feed on the prey of the carnivorous plant and therefore support the degradation of the prey intensively. As the product of their own digestion, the pitcher organisms release inorganic ions which can be absorbed by the plant as nutrients.</p>