Search

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. [ABSTRACT FROM AUTHOR]

The pseudometallophyte Rumex acetosella L. occupies habitats with normal and high soil concentrations of zinc (Zn), lead (Pb), and copper (Cu). It remains unclear if the plants respond to the toxic metals by altering their morphology and increasing the resilience of their cells. We compared plants growing on soils contaminated with Zn/Pb (populations Terézia, Lintich), or Cu (populations Špania Dolina, Staré Hory), with those from non-contaminated soil (Dúbravka) in Slovakia, and analysed leaf structure, physiology, and metal contents by light and electron microscopy, element localization by energy-dispersive X-ray analysis (EDX) in scanning electron microscope, and by specific fluorescence dyes. In control population, the epidermis of the amphistomatic leaves of R. acetosella contained capitate glandular trichomes, consisting of four head (secretory), two stalk, and two basal cells. The ultrastructure of secretory cells revealed fine wall ingrowths bordered by plasma membrane protruding into the cytoplasm. The metallicolous populations had higher contents of Zn and Cu in the epidermal and glandular cells, and a higher density of both stomata and trichomes. Extensive cell wall labyrinth was present in the trichome secretory cells. Their abnormal number and elevated metal contents might indicate effects of heavy metals, especially of Cu, on mitosis and cell plate formation. Differences in leaf physiology were indicated by significantly higher cytoplasmic tolerance to Zn and Cu in metallicolous populations and by structural properties of glandular heads suggesting secretion of toxic metals. Our findings are suggestive of plant reactions to metal stress, which facilitate the populations to occupy the metal-contaminated sites. [ABSTRACT FROM AUTHOR]

The bryophyte Mielichhoferia elongata is known to occur on copper-rich substrate, but the exact resistance level remained to be determined by in vitro experiments. Here, we tested its copper tolerance in graded copper solutions and compared the results to the moss Physcomitrella patens that is not known to inhabit heavy metal sites. Our results confirm the survival of M. elongata in classical resistance experiments of up to 10 mM Cu-ethylenediaminetetraacetic acid (EDTA) solution. Interestingly, P. patens is equally resistant. Cultured on copper-enriched agar plates for over 5 weeks, P. patens survived even higher copper levels of up to 100 mM Cu-EDTA and an increment of growth was detected on all concentrations tested. Obviously, P. patens is able to withstand harmfully high levels of copper in both solution and substrate. In this short communication, we give a detailed description of the growth rates and discuss the results in comparison to other moss species and heavy metals. [ABSTRACT FROM AUTHOR]

We analysed cell wall formation in rapidly growing root hairs of Triticum aestivum under reduced turgor pressure by application of iso- and hypertonic mannitol solutions. Our experimental series revealed an osmotic value of wheat root hairs of 150 mOsm. In higher concentrations (200–650 mOsm), exocytosis of wall material and its deposition, as well as callose synthesis, still occurred, but the elongation of root hairs was stopped. Even after strong plasmolysis when the protoplast retreated from the cell wall, deposits of wall components were observed. Labelling with DiOC6(3) and FM1-43 revealed numerous Hechtian strands that spanned the plasmolytic space. Interestingly, the Hechtian strands also led towards the very tip of the root hair suggesting strong anchoring sites that are readily incorporated into the new cell wall. Long-term treatments of over 24 h in mannitol solutions (150–450 mOsm) resulted in reduced growth and concentration-dependent shortening of root hairs. However, the formation of new root hairs does occur in all concentrations used. This reflects the extraordinary potential of wheat root cells to adapt to environmental stress situations. [ABSTRACT FROM AUTHOR]

Aquatic carnivorous plants of the genus Utricularia capture and utilise a wide range of small aquatic organisms. Most of the literature focuses on animals as prey. In this study, we investigate the occurrence of algae inside the traps of four species of bladderwort. We observed that algae of 45 genera form up to 80% of the total prey; algae were found frequently in traps without animal prey. The majority are coccal and trichal algae of the families Desmidiaceae and Zygnemataceae. The percentage of algae increases significantly with decreasing electric conductivity of the water ( r S = −0.417; P = 0,000). Thus, algae are the most frequent prey in extremely soft waters. The percentage of algae did not differ significantly, not within the investigated Utricularia species or within the various study sites. However, the taxonomic composition of the algal prey showed highly significant differences between different sites. More than 90% of the trapped algae were killed and degraded by the bladders. The recent data allow for two alternative hypotheses: either algal prey supplements animal prey in oligotrophic waters, or the unprofitable trapping of algae is rather an additional stress factor for Utricularia and contributes to its limited distribution in some peat bogs. [ABSTRACT FROM AUTHOR]

Carnivorous 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 [ABSTRACT FROM AUTHOR]

The cortical endoplasmic reticulum (ER) of living onion inner epidermal cells has been studied by video-microscopy. We observed local movements of individual ER membranes, which cause transformations of the polygonal net. Membrane tubules glide along one another, causing transfiguration, reduction and decomposition of polygons. Membrane tubules and lamellae also extend from the existing net and thus increase the amount of ER. These movements occur in close correlation with organelle movements, suggesting a structural coalignment of the net with actin microfilaments (MFs). The membranes in the cortical cytoplasm are not distributed randomly but are tethered to certain domains; even when dislocated, they return to such anchoring points. This was not observed with ER reaching deeper into the cytoplasm. We therefore propose that close associations of ER and the plasma membrane (PM) stabilize the cortical ER and may stabilize coaligning MFs as well. [ABSTRACT FROM AUTHOR]

In epidermal cells of Drosera tentacles that have been preserved for ultrastructural analysis through high pressure freeze fixation and freeze substitution we describe the frequent occurrence of microfilament (MF)-endoplasmic reticulum (ER) complexes. These are found throughout the cytoplasm where they are observed in close association with the plasmalemma (PL), the tonoplast, nuclei, mitochondria, chloroplasts, and microbodies. The MF component of the complexes is identified as actin based on immunogold labelling with actin antibodies. The actin-ER complexes are prominent in the cortical cytoplasm. In this region a network of predominantly tubular ER occupies an intermediary position in which it associates closely with both the PL and the actin MFs. We suggest that the ER, especially those elements adjacent to the PL in the cortical cytoplasm, stabilizes the actin MFs and provides the necessary anchor against which the forces for cytoplasmic streaming are generated. [ABSTRACT FROM AUTHOR]