Search

The current inventory was mainly based on revising herbarium specimens collected since the 19th century and confirmed twenty-one Characeae species in Lithuania. They are representatives of five genera: Chara (12 species), Nitella (5), Tolypella (2), Lychnothamnus and Nitellopsis (by one species each). Thirteen species mentioned in references or labels of herbarium specimens were not confirmed. The occurrence of the Characeae species was recorded in 251 map grid cells (42% of the total number 593). Herbarium specimens were collected from 693 water bodies, mainly lakes. Chara globularis was the most common species, recorded in 150 map grid cells and more than 250 water bodies. Ten species (C. aspera, C. contraria, C. filiformis, C. subspinosa, C. tomentosa, C. virgata, C. vulgaris, Nitella mucronata, N. flexilis, Nitellopsis obtusa) were recorded in the interval from 100 to 50 grid cells and also belong to the group of common species. Chara papillosa and C. strigosa were recorded less than in 50 grid cells and should be considered quite common. Eight species (C. baltica, C. canescens, Lychnothamnus barbatus, Nitella confervacea, N. gracilis, N. syncarpa, Tolypella nidifica, T. prolifera) were recorded in ten or fewer grid cells and belong to the group of rare or very rare species. The occurrence of species that have not been confirmed by the herbarium specimens was discussed. [ABSTRACT FROM AUTHOR]

Re-establishment of submerged macrophytes and especially charophyte vegetation is a common aim in lake management. If revegetation does not happen spontaneously, transplantations may be a suitable option. Only rarely have transplantations been used as a tool to support threatened submerged macrophytes and, to a much lesser extent, charophytes. Such actions have to consider species-specific life strategies. K-strategists mainly inhabit permanent habitats, are perennial, have low fertility and poor dispersal ability, but are strong competitors and often form dense vegetation. R-strategists are annual species, inhabit shallow water and/or temporary habitats, and are richly fertile. They disperse easily but are weak competitors. While K-strategists easily can be planted as green biomass taken from another site, rare R-strategists often must be reproduced in cultures before they can be planted on-site. In Sweden, several charophyte species are extremely rare and fail to (re)establish, though apparently suitable habitats are available. Limited dispersal and/or lack of diaspore reservoirs are probable explanations. Transplantations are planned to secure the occurrences of these species in the country. This contribution reviews the knowledge on life forms, dispersal, establishment, and transplantations of submerged macrophytes with focus on charophytes and gives recommendations for the Swedish project.

Effect of amino acid L-asparagine on electrical signalling of single Nitellopsis obtusa (Characeaen) cell was investigated using glass-microelectrode technique in current-clamp and voltage-clamp modes. Cell exposure for 30 min to 0.1 mM and 1 mM of asparagine resulted in changes of electrically stimulated action potential (AP) parameters in comparison to standard conditions. Results indicate that asparagine acts in dose-dependent manner: increases AP amplitude by hyperpolarizing AP threshold potential (Eth), prolongs action potential repolarization, increases maximum Cl− efflux amplitude along with the increase of activation and inactivation durations. Presented findings provide new aspects of exogenous amino acids' effect on plants' electrical signalling with emphasis on separate single plant cell excitability and AP characteristics. [ABSTRACT FROM AUTHOR]

The change regularity of potential (φm), resistance (Rm) and capacity (Cm) of the plasma membrane (PM) in Nitellopsis obtusa cells under the influence of dimethylsulfoxide (DMSO) have been studied. The investigated cells have φm=-171±3 mV, Rm=3,8±1,6 Om∙m2, Cm=0,92±0,04 mkF∙sm-2 in the standard environmental conditions. The threshold concentration of DMSO 1 ÷ 4 % caused the depolarization of the PM to 20-25mV and increase Cm to 22-26% in the Rm constant. The effective influence of DMSO concentration 1÷ 4% depolarizated PM to the level of -110mV. At first Rm decreased 40%, then occurres its restoration. The final stationary level of Rm was 20% higher than initial one. The value of PM depolarization depended on initial level of φm and the concentration of DMSO in the medium. In that case Cm only increased and its total value was 45% compared with the initial value. In the that work the effects of the solvent are discussed from the point of its influence on the structure state of lipid phase and the transport communications of PM. [ABSTRACT FROM AUTHOR]

Using the liquid microelectrode technique, the electrical potentials of nodal cells and the with them internodal cells neighbouring, of Nitellopsis obtusa plants of the Characeae family were determined. A specific variation in the potential of nodal cells in the form of cacophony-type irregular disturbances was also found, indicating that the node is not a passive mechanical element controlled by internodal cells, but is a complex system of coupled-, and different metabolic oscillators.

Like many other benthic algae, charophytes can attain high abundance in shallow waters, thereby affecting benthic ecology and nutrient cycling, and their subsequent death, detachment, and shoreline deposition contribute to beach fouling within the Laurentian Great Lakes. In-situ nutrient enrichment experiments and stoichiometric analyses have shown that other types of Great Lakes benthic algae are frequently phosphorus (P)-limited, but comparable information is lacking for charophytes. This study coupled short-term P enrichment of charophytes collected from inner Saginaw Bay with fluorometric estimates of algal photosynthesis to assess potential nutrient limitation. Benthic irradiance at the experimental sites was frequently sufficient to saturate charophyte photosynthesis, and charophyte photosynthesis was stimulated by experimental P enrichment, suggesting that these algae were P-limited under natural conditions. Reduction of P loading may be an effective charophyte control measure, even in relatively light-poor and nutrient-rich areas of the Great Lakes. [ABSTRACT FROM AUTHOR]

The distribution and ecology of charophytes in Lubelszczyzna (Eastern Poland) is described based on herbaria collections, literature data, and the author's own investigations. Maps showing the distribution of all 22 charophyte species identified so far are presented, as well as the details of habitats ecology. Some data on species frequency, conservation, and threats are added.

A critical check-list of the Charophytes from the Iberian Peninsula, based on literature records and original data, is presented. It includes 46 taxa, including 26 species, 14 varieties and 6 forms, from 5 genera: Chara, Lamprothamnium, Nitella, Nitellopsis and Tolypella.

Re-establishment of submerged macrophytes and especially charophyte vegetation is a common aim in lake management. If revegetation does not happen spontaneously, transplantations may be a suitable option. Only rarely have transplantations been used as a tool to support threatened submerged macrophytes and, to a much lesser extent, charophytes. Such actions have to consider species-specific life strategies. K-strategists mainly inhabit permanent habitats, are perennial, have low fertility and poor dispersal ability, but are strong competitors and often form dense vegetation. R-strategists are annual species, inhabit shallow water and/or temporary habitats, and are richly fertile. They disperse easily but are weak competitors. While K-strategists easily can be planted as green biomass taken from another site, rare R-strategists often must be reproduced in cultures before they can be planted on-site. In Sweden, several charophyte species are extremely rare and fail to (re)establish, though apparently suitable habitats are available. Limited dispersal and/or lack of diaspore reservoirs are probable explanations. Transplantations are planned to secure the occurrences of these species in the country. This contribution reviews the knowledge on life forms, dispersal, establishment, and transplantations of submerged macrophytes with focus on charophytes and gives recommendations for the Swedish project. [ABSTRACT FROM AUTHOR]

The present investigation on the axial nodes of 32 taxa belonging to the genera Chara, Lamprothamnium, Nitcllopsis, Nitella and Tolypella confirms previous reports that within a given taxonomic group the structure of the main axial nodal complex is highly consistent. Besides the genera Nitella and Tolypella of the tribe Nitelleae, Lamprothamnium of the tribe Chareae is the only genus in which the central cells of the main axial nodal complex subdivide. This anatomical feature of the main axial nodal complex thus clearly separates the genus Lamprothamnium from the other genera of the tribe Chareae. In 2 controversial species of the genus Chara, C. hornemannii and C. buckellii, the present study reveals that the central cells of their main axial nodal complexes do not subdivide. The transfer of these two species to the genus Lamprothamnium by Daily (1) may not be appropriate. [ABSTRACT FROM AUTHOR]

The relationship between adenine-nucleotide levels and metabolism-dependent membrane potential was studied in cells of Nitellopsis obtusa. Effects of ADP and AMP in the presence of ATP on electrogenic pump activity were measured in the dark, using the continuous perfusion method. Both ADP and AMP acte as competitive inhibitors for ATP, the K value for either compound being about 0.4 mM. The role of ADP and AMP as regulating factors for the electrogenic pump was investigated under various metabolic conditions. Application of N gas in the dark caused a significant membrane depolarization amounting to 90 mV, but cytoplasmic streaming and membrane excitability were not affected. Under anoxia, the ATP level decreased from 1.6 to 0.5 mM; ADP increased but only slightly, and AMP increased greatly. However, the time course of changes in the adenine nucleotides was not concurrent with that of the membrane-potential changes, thus, the adenine-nucleotide level changes cannot fully account for the N-elicited depolarization. Under light, although the membrane hyperpolarized, no significant changes in the adenine-nucleotide levels were observed. Therefore, the light-induced membrane hyperpolarization cannot be explained solely by changes in adenine-nucleotide levels. [ABSTRACT FROM AUTHOR]

The temperature dependence of cytoplasmic streaming in intact and tonoplast-free cells of Nitellopsis obtusa was studied using a cryomicroscope. The streaming velocity decreases linearly with decrease in the temperature in well-buffered tonoplast-free cells but non-linearly in some intact cells. These results suggest that low temperature causes a disturbance in the homeostasis of calcium and protons, which inhibit cytoplasmic streaming in intact cells. [ABSTRACT FROM AUTHOR]

Internodal cells of Nitellopsis obtusa were made tonoplast-free by intracellular perfusion of the vacuole with medium containing 5 mM EGTA. Next, the cells were perfused with media of various Ca concentrations and the plasma membrane potential (E) and resistance (R) were measured by the open-vacuole method. In the presence of ATP, 10 M Ca had no effect on E and R but 10 M Ca depolarized E slightly and decreased R a little. Ca at more than 10 M depolarized E drastically (E: about −10 to − 20 mV) and decreased R to almost zero. Even when the electrogenic pump was stopped by removing ATP, the Ca effect was almost the same as that observed in its presence. The maximum depolarization level measured in the presence of more than 10 M Ca was more positive than the peak of the action potential. Therefore, the intracellular concentration of Ca ([Ca]) should not become more than 10 M during excitation. The tonoplast-free cell did not release Cl to the external medium during depolarization induced by high [Ca]. Since no Cl efflux was observed on membrane excitation in the tonoplast-free cell, the question remains of whether or not the depolarization accompanying excitation is caused by a transient increase in [Ca] which was demonstrated by Williamson and Ashley (1982). [ABSTRACT FROM AUTHOR]

The hydraulic resistance was measured on internodal cells of Nitellopsis obtusa using the method of transcellular osmosis. The hydraulic resistance was approximately 2.65 pm sec Pa, which corresponds to an osmotic permeability of 101.75 μm sec (at 20°C). p-Chloromercuriphenyl sulfonic acid ( pCMPS) (0.1-1 mm, 60 min) reversibly increases the hydraulic resistance in a concentration-dependent manner. pCMPS does not have any effect on the cellular osmotic pressure. pCMPS increases the activation energy of water movement from 16.84 to 32.64 kJ mol, indicating that it inhibits water movement by modifying a low resistance pathway. pCMPS specifically increases the hydraulic resistance to exosmosis, but does not influence endosmosis. By contrast, nonyltriethylammonium (C), a blocking agent of K channels, increases the hydraulic resistance to endosmosis, but does not affect that to exosmosis. These data support the hypothesis that water moves through membrane proteins in characean internodal cells and further that the polarity of water movement may be a consequence of the differential gating of membrane proteins on the endo- and exoosmotic ends. [ABSTRACT FROM AUTHOR]

The regulation of voltage-dependent Ca channels by protein phosphorylation and dephosphorylation was studied using tonoplast-free cells of Nitellopsis. Since the Ca-channel activation has a dominant role in the membrane excitation of tonoplast-free cells (T. Shiina and M. Tazawa, J. Membrane Biol. 96:263-276, 1987), it seems to be reasonable to assume that any change of the membrane excitability reflects a modulation of the Ca channel. When agents that enhance phosphoprotein dephosphorylation (protein kinase, inhibitor, phosphoprotein phosphatase-1, -2A) were introduced to the intracellular surface of the plasmalemma (twice-perfused tonoplast-free cells), the membrane potential depolarized and the membrane resistance decreased under current-clamp experiments. By contrast, when cells were challenged with agents that enhance protein phosphorylation (phosphoprotein phosphatase inhibitor-1, α-naphthylphosphate), the membrane potential hyperpolarized, and the membrane resistance increased. When phosphoprotein phosphatase-1 or -2A was perfused, the current-voltage ( I-V) curve which was obtained under ramp voltage-clamp condition exhibited the so-called N-shaped characteristic, indicating an acceleration of the Ca-channel activation. This effect was suppressed by the addition of phosphoprotein phosphatase inhibitors. ATP-γ-S, which is assumed to stimulate protein phosphorylation, decreased the inward current in the I-V curve. The dependence of the Ca-channel activation on intracellular ATP was different between the once-perfused and twice-perfused cells. In once-perfused cells, the membrane excitability was reduced by low intracellular ATP concentration. By contrast, in twice-perfused cells, excitability was enhanced by ATP. [ABSTRACT FROM AUTHOR]

The membrane potential of tonoplast-free cells of Nitellopsis obtusa Graves in relation to the intracellulcar concentration of ATP ([ATP]) was measured using either the ordinary microelectrode method or the open-vacuole method (M. Tazawa, M. Kikuyama and S. Nakagawa, 1975, Plant Cell Physiol. 16, 611). The intracellular ATP concentration was modified in the microelectrode method by introducing into the cell ATP-regenerating media composed of phosphoenolpyruvate and pyruvate kinase, and in the open-vacuole method by continuously perfusing the cell interior with media of known ATP concentrations. Plots of the membrane potential against the [ATP] follow a rectangular hyperbola. Using the microelectrode method, the maximum ATP-dependent potential was about-120-130 mV and the apparent K about 10-30 μM. When the openvacuole method was used, the maximum ATP-dependent potential was about 100 mV and the apparent K about 100 μM. The membrane was still excitable when the [ATP] was 10 μM but not at 1.7 μM [ATP]. The membrane resistance increased in parallel with a decrease in [ATP] or membrane depolarization, but decreased again at a very low [ATP] (1.7 μM). [ABSTRACT FROM AUTHOR]

The structure and development of the bulbils of Chara hornemannii, Chara aspera, Lamprothamnium papulosum, Lamprothamnium succinctum and Nitellopsis obtusa have been studied. [ABSTRACT FROM AUTHOR]

The structure and development of Nitellopsis obtusa have been studied in culture. The main features are compared with those of the other members of the Chareae. [ABSTRACT FROM AUTHOR]

Effects of DO were studied on internodal cells of the freshwater alga Nitellopsis obtusa under plasmalemma perfusion (tonoplast-free cells) with voltage clamp, and on Ca channels isolated from the alga and reconstituted in bilayer lipid membranes (BLM). External application of artificial pond water (APW) with DO as the solvent to the perfused plasmalemma preparation led to an abrupt drop of membrane resistance ( R= 0.12 ±0.03 kΩ · cm), thus preventing further voltage clamping. APW with 25% DO caused a two-step reduction of R: first, down to 2.0 ± 0.8 kΩ · cm, and then further to 200 Ω · cm, in 2 min. It was shown that in the first stage, Ca channels are activated, and then, Ca ions entering through them activate the Cl channels. The Ca channels are activated irreversibly. If 100 m m CsCl was substituted for 200 m m sucrose (introduced for isoosmoticity), no effect of DO on Rwas observed. Intracellular HO/DO substitution also did not change R. In experiments on single Ca channels in BLM HO/ DO substitution in a solution containing 100 m m KCl ( trans side) produced no effect on channel activity, while in 10 m m KCl, at negative voltage, the open channel probability sharply increased. This effect was irreversible. The single channel conductance was not altered after the HO/DO substitution. The discussion of the possible mechanism of DO action on Ca and Cl channels was based on an osmotic-like stress effect and the phenomenon of higher D-bond energy compared to the H-bond. [ABSTRACT FROM AUTHOR]

• In the laboratory N. obtusa germination rate was 87%. • Nitellopsis obtusa bulbil size does not relate to shoot number or size. • Optimal N. obtusa growth was observed in charophyte specific Forsberg's media II under low intensity metal-halide light. Much attention has focused on understanding the growth of Nitellopsis obtusa [(Desvaux) J. Groves] (starry stonewort) through chemical drivers with limited information on light availability. This is important as, in addition to water chemistry, light availability largely controls the distribution, abundance and growth of macroalgae. Therefore, the purpose of this study was to evaluate optimal cultivation conditions for bulbil germination and N. obtusa growth ex-situ by investigating synthetic media types, light types and light intensities. In general, nutrient concentration, light type and light intensity all directly influenced growth and morphology of N. obtusa, however this relationship was complex and multifaceted. Nitellopsis obtusa grew best in low-light, high-macronutrient conditions but, in general, was capable of growing under all conditions evaluated, though demonstrated considerable morphological differences. The information presented in this study can help guide field studies and determine the role of light in N. obtusa growth and physiology. This study will provide a foundation for optimized culturing conditions for N. obtusa. Controlled environment evaluations will be essential to enhance our understanding of the biology of this now endangered (Eurasia) yet newly invasive (North America) macroalga. Information provided by this work may also provide insight into the development of effective management strategies for N. obtusa in North America. [ABSTRACT FROM AUTHOR]