Marianne Peroutka

Traps of carnivorous pitcher plants as a habitat: composition of the fluid, biodiversity and mutualistic activities

BACKGROUND Carnivorous pitcher plants (CPPs) use cone-shaped leaves to trap animals for nutrient supply but are not able to kill all intruders of their traps. Numerous species, ranging from bacteria to vertrebrates, survive and propagate in the otherwise deadly traps. This paper reviews the literature on phytotelmata of CPPs. PITCHER Fluid as a Habitat The volumes of pitchers range from 0·2 mL to 1·5 L. In Nepenthes and Cephalotus, the fluid is secreted by the trap; the other genera collect rain water. The fluid is usually acidic, rich in O(2) and contains digestive enzymes. In some taxa, toxins or detergents are found, or the fluid is extremely viscous. In Heliamphora or Sarracenia, the fluid differs little from pure water. INQUILINE Diversity Pitcher inquilines comprise bacteria, protozoa, algae, fungi, rotifers, crustaceans, arachnids, insects and amphibia. The dominant groups are protists and Dipteran larvae. The various species of CPPs host different sets of inquilines. Sarracenia purpurea hosts up to 165 species of inquilines, followed by Nepenthes ampullaria with 59 species, compared with only three species from Brocchinia reducta. Reasons for these differences include size, the life span of the pitcher as well as its fluid. MUTUALISTIC: Activities Inquilines closely interact with their host. Some live as parasites, but the vast majority are mutualists. Beneficial activities include secretion of enzymes, feeding on the plants prey and successive excretion of inorganic nutrients, mechanical break up of the prey, removal of excessive prey and assimilation of atmospheric N(2). CONCLUSIONS There is strong evidence that CPPs influence their phytotelm. Two strategies can be distinguished: (1) Nepenthes and Cephalotus produce acidic, toxic or digestive fluids and host a limited diversity of inquilines. (2) Genera without efficient enzymes such as Sarracenia or Heliamphora host diverse organisms and depend to a large extent on their symbionts for prey utilization.

The roots of carnivorous plants

AbstractCarnivorous plants may benefit from animal-derived nutrients to supplement minerals from the soil. Therefore, the role and importance of their roots is a matter of debate. Aquatic carnivorous species lack roots completely, and many hygrophytic and epiphytic carnivorous species only have a weakly devel-oped root system. In xerophytes, however, large, extended and/or deep-reaching roots and sub-soil shoots develop. Roots develop also in carnivorous plants in other habitats that are hostile, due to flood-ing, salinity or heavy metal occurance. Information about the structure and functioning of roots of car- nivorous plants is limited, but this knowledge is essential for a sound understanding of the plants’ physiology and ecology. Here we compile and summarise available information on: (1) The morphology of the roots. (2) The root functions that are taken over by stems and leaves in species without roots or with poorly developed root systems; anchoring and storage occur by specialized chlorophyll-less stems; water and nutrients are taken up by the trap leaves. (3) The contribution of the roots to the nutrient supply of the plants; this varies considerably amongst the few investigated species. We compare nutrient uptake by the roots with the acquisition of nutri-ents via the traps. (4) The ability of the roots of some carnivorous species to tolerate stressful conditions in their habitats; e.g., lack of oxygen, saline conditions, heavy metals in the soil, heat during bushfires, drought, and flooding

Deadly Glue — Adhesive Traps of Carnivorous Plants

Carnivorous plants trap and utilize animals in order to improve their supply with mineral nutrients. One strategy for prey capture is the use of adhesive traps, i.e., leaves that produce sticky substances. Sticky shoots are widespread in the plant kingdom and serve to protect the plant, especially flowers and seeds. In some taxa, mechanisms have been developed to absorb nutrients from the decaying carcasses of animals killed by the glue. In carnivorous plants sensu stricto, additional digestive enzymes are secreted into the glue to accelerate degradation of prey organisms.

Ecophysiological observations on Drosophyllum lusitanicum

The carnivorous plant Drosophyllum lusitanicum inhabits heathland and ruderal sites in Portugal, Spain and Morocco. In the literature, various theories have been discussed concerning the ability of Drosophyllum to survive the annual dry period in summer. In August 2004, we examined: (1) the microclimate, (2) soil parameters and (3) the physiological conditions of the plants on two sites in Portugal and Spain. First, during the day, plants are exposed to very high air and soil temperatures and very low air humidity. The climatic extremes are not significantly softened by the population, only the wind speed is drastically decreased. During the night, on the other hand, very high air humidity and dew formation could be observed. The harsh climate is accompanied by stressful soil conditions. Second, the soil is completely dry, poor in fine earth, calcium and nutrients and more or less acid. Third, in spite of these climatic and edaphic extremes, all plants were green, produced trapping mucilage and caught numerous animals. Far from being affected by these conditions, Drosophyllum showed even better growth and reproduction on more extreme sites. We analysed the root system and found living fine roots missing. The osmotic value of the plants is rather low and water storage organs are absent. Therefore we conclude that in summer Drosophyllum is nourished by the dew at night.

Glands of carnivorous plants as a model system in cell biological research

Abstract We use glands of carnivorous plants to investigate the cyto-architecture and the physiology of secreting and absorbing plant cells. Accordingly we apply life cell microscopy, e.g. video enhanced light microscopy and ultraviolet microscopy, and combine it with electron microscopy of cryo-fixed material. In Drosera capensis, Byblis liniflora and Nepenthes *coccinea, we analyse (1) the Golgi apparatus and its vesicles during formation and secretion of trapping mucilage, (2) the endoplasmic reticulum producing digestive enzymes, (3) digestive uptake and (4) the movement of organelles along the cytoskeleton. These observations improve our understanding of the structure and function of carnivorous plants; in addition, they advance our general conception of the cell biology of glandular cells in plants.

Metalloid Contaminated Microhabitats and their Biodiversity at a Former Antimony Mining Site in Schlaining, Austria

This paper is on the biological impact of arsenic and antimony on the flora and microflora on a former Sb- mining site in Schlaining (Stadtschlaining, Burgenland, Austria). Several habitats were investigated with respect to biodi- versity and metalloid contamination in soil. Although the overburden of the mining activity had been remediated less than ten years ago, metalloid concentrations occurred in soil up to 1.4‰ As and 3.6% Sb, respectively, in some microhabitats, as determined by Instrumental Neutron Activation Analysis. These metalloids were embedded into a nonuniform minera- logical background. Metalloid mobility could not be explained by common models, indicating that predictions on the mo- bility of geogenic metalloids require additional mineralogical data. The biological effects of this contamination were vari- able. We observed that metalloid resistant strands of microorganisms appeared in the contaminated soil. In cultivation ex- periments, Sb was found to be more toxic than As. Sulphur oxidising strand were more resistant than organotrophic ones and grew even better on cultivation media spiked with 10 ppm As than on the unspiked control. The flora was only par- tially influenced: the lowest biodiversity was found in metalloid richest soils, but moderate contamination resulted in en- hanced species numbers. Only in one case, where the pH-buffering capacity of the soil was exceeded by consumption of the entire carbonate, no embryophytes occurred. This was probably due to extreme pH conditions as well as to metalloid concentrations. Our data support the hypothesis that higher plants are rather affected by extreme soil conditions, which of- ten coincide with As contaminations, than by the contamination itself. A small rivulet in this area contained 26 � g/l and thus exceeded the WHO guideline value for As in drinking water by a factor of 2.6. Indeed we observed a diminished bio- diversity in this rivulet.