Capture of algae promotes growth and propagation in aquatic Utricularia.

BACKGROUND AND AIMS: Some carnivorous plants trap not only small animals but also algae and pollen grains. However, it remains unclear if these trapped particles are useless bycatch or whether they provide nutrients for the plant. The present study examines this question in Utricularia, which forms the largest and most widely spread genus of carnivorous plants, and which captures prey by means of sophisticated suction traps. METHODS: Utricularia plants of three different species (U. australis, U. vulgaris and U. minor) were collected in eight different water bodies including peat bogs, lakes and artificial ponds in three regions of Austria. The prey spectrum of each population was analysed qualitatively and quantitatively, and correlated with data on growth and propagation, C/N ratio and δ(15)N. KEY RESULTS: More than 50 % of the prey of the Utricularia populations investigated consisted of algae and pollen, and U. vulgaris in particular was found to capture large amounts of gymnosperm pollen. The capture of algae and pollen grains was strongly correlated with most growth parameters, including weight, length, budding and elongation of internodes. The C/N ratio, however, was less well correlated. Other prey, such as moss leaflets, fungal hyphae and mineral particles, were negatively correlated with most growth parameters. δ(15)N was positively correlated with prey capture, but in situations where algae were the main prey objects it was found that the standard formula for calculation of prey-derived N was no longer applicable. CONCLUSIONS: The mass capture of immotile particles confirms the ecological importance of autonomous firing of the traps. Although the C/N ratio was little influenced by algae, they clearly provide other nutrients, possibly including phosphorus and trace elements. By contrast, mosses, fungi and mineral particles appear to be useless bycatch. Correlations with chemical parameters indicate that Utricularia benefits from nutrient-rich waters by uptake of inorganic nutrients from the water, by the production of more traps per unit of shoot length, and by the capture of more prey particles per trap, as nutrient-rich waters harbour more prey organisms.

Endocytotic uptake of nutrients in carnivorous plants.

Carnivorous plants trap, digest and absorb animals in order to supplement their mineral nutrition. Nutrients absorbed by the plant include different nitrogen species, phosphate, potassium, trace elements and small organic compounds. Uptake is usually thought to be performed via specific channels, but this study provides evidence that endocytosis is involved as well. Traps of the carnivorous plants Nepenthes coccinea, Nepenthes ventrata, Cephalotus follicularis, Drosophyllum lusitanicum, Drosera capensis, Dionaea muscipula, Aldrovanda vesiculosa, Genlisea violacea × lobata, Sarracenia psittacina and Sarracenia purpurea were stained with methylene blue in order to identify possible sites of uptake. The permeable parts of the traps were incubated with fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) and other fluorescent endocytosis markers, combined with the soluble protein BSA or respiratory inhibitors. Uptake was studied by confocal microscopy. In Nepenthes, small fluorescent vesicles became visible 1 h after incubation with FITC-BSA. These vesicles fused to larger compartments within 30 h. A similar behaviour was found in the related genera Drosera, Dionaea, Aldrovanda and Drosophyllum but also in Cephalotus with glands of different evolutionary origin. In Genlisea and Sarracenia, no evidence for endocytosis was found. We propose that in many carnivorous plants, nutrient uptake by carriers is supplemented by endocytosis, which enables absorption and intracellular digestion of whole proteins. The advantage for the plant of reducing secretion of enzymes for extracellular digestion is evident.

Quantification of Protein Uptake by Endocytosis in Carnivorous Nepenthales.

Carnivorous plants adsorb prey-derived nutrients partly by endocytosis. This study quantifies endocytosis in Drosophyllum lusitanicum, Drosera capensis, Drosera roseana, Dionaea muscipula and Nepenthes × ventrata. Traps were exposed to 1% fluorescent-labeled albumin (FITC-BSA), and uptake was quantified repeatedly for 64 h. Formation of vesicles started after ≤1 h in adhesive traps, but only after 16 h in species with temporary stomach (D. muscipula and N. × ventrata). In general, there are similarities in the observed species, especially in the beginning stages of endocytosis. Nonetheless, further intracellular processing of endocytotic vesicles seems to be widely different between species. Endocytotic vesicle size increased significantly over time in all species except in D. capensis. Fluorescence intensity of the endocytotic vesicles increased in all species except D. muscipula. After 64 h, estimates for FITC-BSA absorption per gland ranged from 5.9 ± 6.3 ng in D. roseana to 47.8 ± 44.3 ng in N. × ventrata, demonstrating that endocytosis substantially contributes to the adsorption of prey-derived nutrients.

Uptake of Radionuclides by Bryophytes in the Chornobyl Exclusion Zone.

The "Chernobyl nuclear disaster" released huge amounts of radionuclides, which are still detectable in plants and sediments today. Bryophytes (mosses) are primitive land plants lacking roots and protective cuticles and therefore readily accumulate multiple contaminants, including metals and radionuclides. This study quantifies 137Cs and 241Am in moss samples from the cooling pond of the power plant, the surrounding woodland and the city of Prypiat. Activity concentrations of up to 297 Bq/g (137Cs) and 0.43 Bq/g (241Am) were found. 137Cs contents were significantly higher at the cooling pond, where 241Am was not detectable. Distance to the damaged reactor, amount of original fallout, presence of vascular tissue in the stem or taxonomy were of little importance. Mosses seem to absorb radionuclides rather indiscriminately, if available. More than 30 years after the disaster, 137Cs was washed out from the very top layer of the soil, where it is no more accessible for rootless mosses but possibly for higher plants. On the other hand, 137Cs still remains solved and accessible in the cooling pond. However, 241Am remained adsorbed to the topsoil, thus accessible to terrestrial mosses, but precipitated in the sapropel of the cooling pond.

Snatching Sundews-Analysis of Tentacle Movement in Two Species of Drosera in Terms of Response Rate, Response Time, and Speed of Movement.

Drosera, Droseraceae, catch prey with sticky tentacles. Both Australian Drosera allantostigma and widespread D. rotundifolia show three types of anatomically different tentacles: short, peripheral, and snap-tentacles. The latter two are capable of fast movement. This motion was analysed after mechanical, chemical, and electrical stimulation with respect to response rate, response time, and angular velocity of bending. Compared to D. rotundifolia, D. allantostigma responds more frequently and faster; the tentacles bend with higher angular velocity. Snap-tentacles have a lower response rate, shorter response time, and faster angular velocity. The response rates for chemical and electrical stimuli are similar, and higher than the rates for mechanical stimulus. The response time is not dependent on stimulus type. The higher motility in D. allantostigma indicates increased dependence on mechanical prey capture, and a reduced role of adhesive mucilage. The same tentacle types are present in both species and show similar motility patterns. The lower response rate of snap-tentacles might be a safety measure against accidental triggering, since the motion of snap-tentacles is irreversible and tissue destructive. Furthermore, tentacles seem to discern stimuli and respond specifically. The established model of stereotypical tentacle movement may not fully explain these observations.

The Arsenic-Antimony Creek at Sauerbrunn/Burgenland, Austria: A Toxic Habitat for Amphibians.

(1) Background: All Austrian amphibians are affected by the degradation of habitats. Mining contributes to habitat destruction by the formation of spoil heaps and mine drainage waters. In Stadtschlaining/Burgenland, antimony mining led to increased arsenic (As) and antimony (Sb) concentrations in soil and water. This study investigates a contaminated creek, still inhabited by amphibians. (2) Methods: Water and soil were analyzed along the creek and correlated with the occurrence of amphibians. (3) Results: As and Sb were increased, with up to 49,000 mg/kg As and 2446 mg/kg Sb in the soil. Up to 317 mg/kg As and 156 mg/kg Sb became bioavailable under gastric, and up to 298 mg/kg As and 30 mg/kg Sb under intestinal conditions, and were absorbed upon ingestion of soil. Larvae of Salamandra salamandra were found throughout the creek; survival rates were low. Rana temporaria occurs in the most contaminated sections but does not propagate here. Bombina variegata appears occasionally. Amphibians seem not to be able to detect and avoid metal or metalloid contamination. (4) Conclusion: Survival of larvae is dubious, but adult amphibians survive without apparent damage under severe metalloid contamination.

Gland cell responses to feeding in Drosera capensis, a carnivorous plant.

Glands of Drosera absorb and transport nutrients from captured prey, but the mechanism and dynamics remain unclear. In this study, we offered animal proteins in the form of fluorescent albumin (FITC-BSA) and observed the reactions of the glands by live cell imaging and fluorescence microscopy. The ultrastructure of these highly dynamic processes was also assessed in high-pressure frozen and freeze substituted (HPF-FS) cells. HPF-FS yielded excellent preservation of the cytoplasm of all cell types, although the cytosol looked different in gland cells as compared to endodermoid and stalk cells. Especially prominent were the ER and its contacts with the plasma membrane, plasmodesmata, and other organelles as well as continuities between organelles. Also distinct were actin microfilaments in association with ER and organelles. Application of FITC-BSA to glands caused the formation of fluorescent endosomes that pinched off the plasma membrane. Endosomes fused to larger aggregates, and accumulated in the bulk cytoplasm around the nucleus. They did not fuse with the cell sap vacuole but remained for at least three days; in addition, fluorescent vesicles also proceeded through endodermoid and transfer cells to the epidermal and parenchymal cells of the tentacle stalk.

Endocytosis and Digestion in Carnivorous Pitcher Plants of the Family Sarraceniaceae.

Highly evolved carnivorous plants secrete digestive enzymes for degradation of trapped animals and absorb whole macromolecules from their prey by means of endocytosis. (1) Background: In the pitcher-plant family Sarraceniaceae, the production of enzymes is dubious and no evidence for endocytosis is known so far. (2) Methods: Heliamphora nutans, Darlingtonia californica, and nine taxa of Sarracenia are tested for cuticular pores, and for protease and endocytosis of the fluorescent protein analogue FITC-BSA, after 10-48 h of stimulation. (3) Results: Cuticular pores as a prerequisite for enzyme secretion and nutrient uptake are present in all tested species. Permeable cells form clusters in the inner epidermis of the pitchers, but are only little differentiated from impermeable epidermis cells. Proteases are found in S. psittacina, S. leucophylla, S. minor, S. oreophila, S. alabamensis, H. nutans, D. californica lacking only in S. flava and in S. purpurea ssp. purpurea, S. purpurea ssp. venosa, S. rosea, where enzyme production is possibly replaced by degradation via the extraordinary diverse inquiline fauna. S. leucophylla, S. minor, S. oreophila exhibit both protease production and endocytosis; S. psittacina, S. alabamensis, H. nutans, D. californica produce proteases only; no single species shows endocytosis without protease production. (4) Conclusions: Protease secretion seems to be a prerequisite for endocytotic nutrient uptake. Transport of FITC-BSA absorbed by endocytosis towards the vascular tissue of the trap leaves suggests that endocytosis of nutrients is more than a side effect of enzyme secretion.