Chara Vulgaris Research Articles

Comparison of the duration of the cell cycle in successive generation of synchronously dividing antheridial filaments of Chara vulgaris L. as measured with 3H thymidine

Duration of the cell cycle in synchronously dividing cells of successive generation of antheridial filaments in <i>Chara vulgaris</i> L. was estimated on-the basis of labeling with <sup>3</sup>H thymidine. Duration of the cell cycle is proportional to the volume of cells and with their decreasing in the consequence1 of consecutive divisions, the cell cycle becomes shorter. In the 2-, 4-, 8-, and 16-cell generations the length of the S period remains constant, so the duration of the G2 period is gradually reduced.

Influence of the light factor on the course of the cell cycle in the successive generations of the antheridial filaments of Chara vulgaris L.

The exposure to continuous light causes a rise of the mitotic index in the successive generations of the antheridial filaments of <i>Chara vulgaris</i>, whereas culture in darkness leads to a considerable depression of mitosis, and if prolonged, to its complete cessation. Light reverses the effect of the depression of mitosis caused by darkness: in the 16-, and 32-cell generations mitotic activity reappeares as early as after 3 h, but in the 2-, 4-, and 8-cell generations only after 18 h. The size of the cells in the antheridial filaments of plants exposed to continuous illumination is larger as compared with the control material. After being kept in darkness the cells become smaller. The analysis of the size of the latter suggests the inhibition of growth in initial and final periods of interphase. In all generations continuous light reduces the duration of the cell cycle while darkness protracts it. The duration of S phase is similar in all generations of antheridial filaments (ca. 16 h) and is not modified by the light conditions. Thus, the light factor seems to interfere mainly with G2 phase, and its role in the regulation of the cell cycle is correlated with the duration of this phase. The role of light in the kinetics of the cell cycle of the particular generations of antheridial filaments in Chara is discussed in the aspect of the nutritional requirements of cells, hormonal regulation and phytochrome.

Autoradiographic study of 3H colchicine binding in synchronously dividing cells of antheridial filaments of Chara vulgaris L. during successive stages of development

The intensity of <sup>3</sup>H colchicine binding was investigated autoradiographically as a marker of an amount of the microtubule subunits during interphase and mitosis in synchronously dividing 4-, 8-, 16- and 32-celled antheridial filaments of <i>Chora vulgaris</i>. These cells were incubated with 3H colchicine in vivo or after fixation. The radioactivity of cells in the successive generations of antheridial filaments diminishes, similarly as the surface of cytoplasm and intensity of protein synthesis. During interphase the intensity of <sup>3</sup>H colchicine binding is proportional to the increase of cytoplasmic surface; the highest increase of radioactivity occurs in G<sub>2</sub>. During mitosis the increase of radioactivity continues in prophase; the highest radioactivity was found in prophase and telophase cells, the lowest in anaphase cells; a comparatively pronounced radioactivity is visible in metaphase. Radioactivity in posttelophase, as estimated per one daughter cell, is approximately one half of that of the mother cells in telophase of the previous generation suggesting the reutilization of microtubule proteins in the next mitotic cycle.

Dynamic aspects of spermiogenic chromatin condensation patterning by phase separation during the histone-to-protamine transition in charalean algae and relation to bryophytes

During early-to-middle spermiogenesis in multicellular, internally fertilizing charalean green algae (Chara fibrosa, Chara vulgaris, Chara tomentosa, Nitella missouriensis), patterning of chromatin/nucleoplasm in developing spermatid nuclei changes from granules → fibers → contorted lamellae → condensed chromatin. Cytochemical, immunocytochemical, electrophoretic studies on C. vulgaris and C. tomentosa spermatids (Kwiatkowska, Poplonska) and amino acid analysis of protamines in Chara corallina sperm (Reynolds, Wolfe), indicate that more positively charged protamines replace histones directly during spermiogenesis, not indirectly through other intermediate transitional proteins as in internally fertilizing neogastropods and sharks with more ordered spermatid lamellae. We hypothesize that such lamellar-mediated patterning is due to liquid-liquid phase separation by spinodal decomposition. This is a spontaneous thermodynamic process that involves diffusive instability of a lamellar chromatin network, a dominant pattern repeat distance and bicontinuity of chromatin/nucleoplasm phases. C. vulgaris sperm show contorted lamellae in the posterior region, whereas C. corallina sperm display contorted peripheral lamellae and interior fibrils. Among internally fertilizing liverworts, which may have evolved from Zygnematales, mid-spermatid nuclei lack lamellae. Instead they display self-coiled chromatin rods in Blasia pusilla, contain short chromatin tubules in Haplomitrium hookeri resembling those in internally fertilizing mosses and a hornwort and indirectly replace histones with protamines in Marchantia polymorpha.

Effects of UVB radiation exposure from the molecular to the organism level in macrophytes from shallow Mediterranean habitats

The available data on the effects of UVB radiation (UVBR) are scarce for submerged macrophytes, particularly charophytes. We studied the effects of UVBR on Chara baltica, Chara hispida, Chara vulgaris, Nitella hyalina and Myriophyllum spicatum, collected from shallow Mediterranean waterbodies. In a short-term laboratory experiment, we subjected these species to three different UVBR treatments corresponding to daily biologically effective integrated doses of 0, 1 and 6kJm−2. The analysed response variables were DNA damage, UV-absorbing compounds (both the methanol-soluble–SUVACs- and, for the first time in charophytes, the methanol-insoluble cell wall-bound fraction–WUVACs-), the stoichiometric composition, photosynthetic pigments, metabolic and growth rates and morphological architecture. UVBR induced harmful effects on DNA in all species, but M. spicatum appeared to be the most sensitive. The observed DNA damage only appeared to be UVB-dose dependent for C. vulgaris. The charophytes produced higher WUVACs levels and the angiosperm higher SUVACs levels. Higher chlorophyll and carotenoid concentrations were detected in the presence of UVBR, but their ratio was not modified by the applied treatments. The Chl a/b ratio decreased under UVBR in two charophyte species, whereas it increased in the angiosperm, which also exhibited a greater photosynthetic response. Relative growth rates were negatively influenced by UVBR, although the degree of this influence depending on the dose was different among species. UVBR modified growth patterns, particularly in those species exhibiting apical growth. We observed more species-specific differences than commonalities in the effects of and responses to UVBR across the investigated species.

Habitat requirements of charophytes—Evidence of species discrimination through distribution analysis

Charophytes play an important role in aquatic ecosystems but there is a lack of knowledge on the ecology of these macroalgae. Our aim was to characterise the habitat of 12 charophyte species from 78 sites in Switzerland characterised by a set of environmental variables considered critical to the physiology and survival of these plants (climate, land-use, morphometry and chemistry). We searched (i) to evaluate how environmental gradients explain the distribution of species; and (ii) to identify if some species have narrower habitat range than others (“specialist” vs “generalist” species). The Outlying Mean Index (OMI) measures the distance between the mean habitat conditions used by a given species and the mean habitat conditions of all studied waterbodies and was used to analyse the distribution of species. Waterbody size, conductivity and altitude were the most discriminating habitat variables of 7 of the 12 species, followed by calcium and total phosphorus. Chara strigosa is considered a specialist of cold oligotrophic hard waters, and three as generalists (Chara contraria, Chara globularis, Chara vulgaris) with respect to our set of charophyte sites. We demonstrate that charophyte species occur together in a narrow environmental envelope but do not occupy exactly similar habitats. Despite a discrepancy among absolute optima of species in different countries, the relative position of species is likely to be transferable to other regions. Improving our understanding about the ecology of charophyte species by considering a broader scale dataset and more fine-scale biotic and abiotic factors is proposed as an important perspective.

Etoposide interferes with the process of chromatin condensation during alga Chara vulgaris spermiogenesis

DNA topoisomerase II plays an essential role in animal spermiogenesis, where changes of chromatin structure are connected with appearance of transient DNA breaks. Such topo II activity can be curtailed by inhibitors such as etoposide and suramine. The aim of the present study was to investigate, for the first time, the effect of etoposide on spermatid chromatin remodeling in the green alga Chara vulgaris. This inhibitor prolonged the early spermiogenesis stages and blocked the formation of the phosphorylated form of histone H2AX at stages VI–VII. The lack of transient DSBs at these stages impairs the elimination of supercoils containing nucleosomes which lead to disturbances in nucleoprotein exchange and the pattern of spermatid chromatin fibrils at stages VI–VIII. Immunofluorescent and ultrastructural observations revealed that during C. vulgaris spermiogenesis topo II played an important role similar to that in mammals. Some corresponding features had been pointed out before, the present studies showed further similarities.

Effects of Spirogyra arcta on biomass and structure of submerged macrophyte communities

AbstractThe presence of algae can greatly reduce the amount of light that reaches submerged macrophytes, but few experimental studies have been conducted to examine the effects of algae on biomass and structure of submerged macrophyte communities. We constructed communities with four submerged macrophytes (Hydrilla verticillata, Egeria densa, Ceratophyllum demersum, and Chara vulgaris) in three environments in which 0 (control), 50 and 100% of the water surface was covered by Spirogyra arcta. Compared to the control treatment, the 100% spirogyra treatment decreased biomass of the submerged macrophyte communities and of all the four macrophytes except C. demersum. Compared to the control and 50% treatments, the 100% treatment significantly increased relative abundance of C. demersum and decreased that of E. densa. Therefore, the presence of S. arcta can greatly affect the productivity and alter the structure of submerged macrophyte communities. To restore submerged macrophyte communities in conditions with abundant algae, assembling communities consisting of C. demersum or similar species may be a good practice.

Effect of gibberellic acid on the formation and development of antheridia and oogonia in Chara vulgaris L.

The experiments were performed on <em>Chara vulgaris</em> thalli cultivated in axenic conditions. It has been found that application of GA<sub>3</sub> at concentrations of 10<sup>-9</sup> -10<sup>-4</sup> M has no effect on the numbers of developing antheridia and oogonia. GA<sub>3</sub> stimulates the gemmation of capitular cells thus increasing the number of filaments in antheridia (by 45% when 10<sup>-8</sup> M is used). The number of mitotic cycles preceding the differentiation of spermatozoids is not significantly modified by this gibberellin. The number of spermatozoids in antheridia increases by about 20% when 10<sup>-8</sup> -10<sup>-6</sup> M GA<sub>3</sub> concentrations are used. GA<sub>3</sub> shortens the duration of spermatogenesis (by 2.5 days, at 10<sup>-7</sup> M concentration). This effect is due to a shortening of the mitotic cycles in filaments. On the other hand, the time of spermatozoid differentiation, which in the control material lasts about 5.3 days, is not changed significantly by GA<sub>3</sub>. GA<sub>3</sub> hastens the maturation of oogonia and the formation of oospores - both effects are proportional to the GA<sub>3</sub> concentration used.

How a New Locality of Algal Community in the Negev Desert, Israel was Formed

How a New Locality of Algal Community in the Negev Desert, Israel was Formed This is the first study of new locality the Neot Zmadar with charophyte algae in the Negev Desert, Israel revealing the algal diversity and providing an ecological assessment of the habitat by bio-indication methods. Altogether thirty four species of algae were found including macro-algae Chara vulgaris L. in massive growth. Bio-indication and chemical variables characterize the charophyte site environment as oligotrophic to mesotrophic with prevailing of benthic type of organisms of autotrophic type of nutrition, mostly attached of substrate and preferring slow streaming water of temperate temperature, low salinity, low alkalinity, and low to middle organic pollution, the water quality Class II-III. The algal community and water quality show the organic and other contaminants increasing from the upper Pool 2 to lower Pool 3. The charophyte community is one of a few in the Negev with roundyear development, and the population is relatively old, since 1989. We found species-specific features of Chara vulgaris to be well developed under high insolation. The Neot Zmadar stream system is recommended for monitoring of charophyte community in unique anthropogenic aquatic object under increasing insolation impact, with Chara vulgaris as climatic indicator of resistance to sunlight intensity.

The effect of cadmium on growth of vegetative thallus and development of generative organs of Chara vulgaris L. after short time of cultivation

The effect of cadmium ions in two different concentrations (10<sup>-8</sup>M i 10<sup>-6</sup>M) on vegetative thallus, male (antheridia) and femele (oogonia) generative organs of <em>Chara vulgaris</em> L. was investigated. After 9 days of growth in a presence of cadmium the number of lateral branches decreased and the lengths of internodes of the main axis and pleuridia became shortened. The increase in oospores volume and decrease in antheridial volume (both total and internal) after 3, 7 and 9 days of cultivation were observed. The productivity of antheridium measured by the number of antheridial filaments and number of cells within filament is also lower in plants cultivated with cadmium in comparison with control ones.

PCC-like induction of mitosis in Chara vulgaris antheridia initiating differentiation of spermatozoids in the darkness

The objects of this research were the antheridial filament cells of <em>Chara vulgaris</em> which after 5-day mitodepressing treatment of the darkness reactivated mitosis (without light stimulation) in the result of the physiological state evocing the initiation of spermiogenesis in the antheridium. The course of these divisions was observed in relation to control cells cultivated in the natural photoperiod L:D = 14:10. It was shown that the passage of dark-arrested cells from early G<sub>2</sub> (VII stage) to the early prophase in the cells linked to the base of filaments by plasmodesmata with spermatids initiating spermiogenesis, resembles the prematuraly condensed chromosomes (PCC). In this way a by-pass of the cells in the stage VII to early prophase occurs without reconstruction of granular components of nucleoli and with condensed stage of mitochondria characterising the dark-arrested cells. In opposition to this phenomenon in the control cell cycle and in light-induced reactivation of mitosis in the dark-arrested cells, initiation of the prophase follows the series of changes of the nuclear ultrastructure (VIII stage - decondensation of chromatin, IX and X stages nuclei with reticulate chromatin). At the early prophase, irrespective of the physiological conditions, the electron-transparent space appears between nuclear envelope and the chromatin as the effect of solublisation of lamins. The fine fibrils pass this space and link chromatin to the inner nuclear membrane.

Size-variation in the antheridia and oogonia of Chara vulgaris under different experimental conditions

Changes in sizes and shapes of sex organs - antheridia and oogonia - were studied in wild populations of <em>Chara vulgaris</em> collected during summer, autumn, and from samples cultured in the laboratory under varying L:D and temperature conditions. Morphometric measurements indicate that the size variations refer mainly to male sex organs, while those evidenced for oogonia are much lower. Our observations are discussed in terms of changing morphogenetic preferences for antheridia and oogonia within the life-span of a plant.

Changes in the number and size of nucleoli of Chara vulgaris L. antheridial filament cells during the period preceding light-induced re-initiation of cell divisions following a mitodepressive effect of darkness

The changes in number and size of nucleoli of <em>Chara vulgaris</em> antheridial filament cells were monitored with the use of Howell and Black's silver staining method. After a 3-day mitodepressive treatment with darkness the cells were exposed to light which reactivated mitotic activity after 18-20 hours. Eight-celled antheridial filaments were observed. In the period preceding light-induced re-initiation of mitoses a gradual reconstruction of the number and size of nucleoli characteristic of control, as well as their total area per nucleus appeared. The obtained results indicate that one of the important conditions for a cell to be able to divide is accumulation of nucleolus components characteristic of a given developmental stage and this controls nucleologenesis of the subsequent cell cycle.

Effect of kinetin on the course of cell cycle in successive developmental stages of the antheridial filaments of Chara vulgaris L.

Effects of kinetin on the course of cell cycle in successive developmental stages of the antheridial filaments of <em>Chara vulgaris</em> L. were investigated. A shortening of the duration of cell cycles has been observed, particularly in initial. and final developmental stages. S phase. shortened in all stages whereas G<sub>2</sub> phase+mitosis shortened in early but become longer in late developmental stages of filaments. Incorporation of <sup>14</sup>C-adenine into cell nuclei increased after kinetin treatment in 4- and 8-celled filaments whereas that of <sup>3</sup>H-phenylalanine increased in 8- and particularly 16-celled ones. This plant growth regulator stimulated also the <sup>3</sup>H-thymidine incorporation into cells in studied developmental stages of filaments. The stimulation of radioactive phenylalanine incorporation into nucleus and cytoplasm was stronger in late G<sub>2</sub> phase. A participation of cytokinins in the control of cell cycle in relation to process of differentiation of antheridial cells is discussed. A possibility of changes in the cytokinin content in antheridia and antheridial filament cells during their; development has been postulated.

Callose formation in injured cells of the vegetative and generative thallus of Chara vulgaris L. Absence of callose in the process of cytodifferentiation

In an alga <em>Chara vulgaris</em> L. the processes of differentiation of vegetative system cells of the thallus, and initiation and development of generative organs are not associated with callose formation. It was demonstrated that damage to any of the somatic cells and also generative and nongenerative cells of the antheridium and oogonium are capable of callose formation independently of their developmental stage. The localisation and thickness of these layers depend on the way the cells are injured and on their size. The protective role of callose in such cells may consist, beside strengthening the damaged walls, in protection of the symplast by formation of callose deposits on the walls with plasmodesmata; it may also consist in increasing the water potential of the cells. Experiments in which callose deposition was provoked by pressing of the cells or damage leading to a sudden increase of the water potential of the extracellular environment suggest that a sudden increase of tension in the cells may be a factor triggering the "callose effect".

Velocity of cytoplasm streaming in basal and subbasal cells of antheridium as well as internodal cells of pleuridium in Chara vulgaris L. and GA3 influence on it: videomicroscopic observations

The velocity of cytoplasm streaming in an antheridial basal cell and in a subbasal cell as well as in internodal cells of pleuridia carrying antheridia were measured with the use of videomicroscopy. Velocity of streaming proved different depending on a cell type. The most intensive streaming (ca 40 µm/s) was observed in a subbasal cell while in a basal cell it was quite intensive during antheridial filament cells proliferation but falling to half of it during spermatozoid differentiation (ca 20 µm/s and 10 µm/s respectively). In internodal cells of pleuridia the velocity was ca 17 µm/s. GA<sub>3</sub> at the 10<sup>-5</sup>M concentration decreased the velocity of streaming in a basal cell during proliferation of antheridial filament cells and increased it during spermiogenesis. In internodal cells of pleuridia the velocity diminished while in a subbasal cell it rose a little after GA<sub>3</sub> administering. The obtained data suggest that cytoplasm streaming and its reaction to exogenous gibberellin depend on the role of a cell in a multicellulate system; it also depends on a developmental stage.

The effect of light factor on the development of thallus and generative organs in Chara vulgaris L.

During long-term axenic culture of Chara continuous illumination (L=24) increases mitotic activity of almost all types of cells. In such conditions only initiation of oogonia is inhibited, leading into a strong predomination of male generative organs. Prolonged darkness (L:D=1:23) exerts a mitodepressing effect. Oogonia and antheridia are especially susceptible to the reduction of the light period. Modifications of the elongating growth in various photoperiods are different in the polyploid regions of the vegetative thallus and in haploid cells of the antheridial filaments. Segments of both axial internodes and lateral pleuridia increase their dimensions at L:D=1:23, whereas at L=24 their growth is significantly inhibited. Different reaction is noted in the cells of antheridial filaments: at L=24 they are about 10% longer than in the control (L:D=14:10). The duration of the antheridium aevelopment, from the stage of unicellular filaments to the moment of antheridium opening, is 1.5 days shorter at L=24 as compared with the control. This shortening includes proportionally both the period of divisions within antheridial filaments and the period of spermatozoid differentiation.

Studies on the role of gibberellins in the regulation of spermatogenesis in Chara vulgaris L.

Antheridia from isolated nodes of Chara vulgaris, developing in the presence of either AMO-1618 or GA<sub>3</sub>, were studied. AMO-1618 which lowers the level of endogenous gibberellins causes a significant, proportional to the concentration, reduction in: 1) the number of antheridial filaments formed in antheridia, 2) spermatid number within a filament, as a result of eliminating one mitotic division at the first stage of spermatogenesis. Exogenous GA<sub>3</sub> at the concentration 10<sup>-5</sup> M evokes opposite effect i.e. increase in the number of antheridial filaments and increase in the number of spermatids within filament. Total number of spermatids within an antheridium decreases under the influence of 10<sup>-4</sup>M AMO-1618 three times in comparison with the control, whereas it increases twice following 10<sup>-5</sup>M GA<sub>3</sub> treatment. It has been suggested that the normal course of spermatogenesis requires precisely determined level of endogenous gibberellins.

The effects of pulse cycloheximide treatments on the light-induced recovery of mitotic divisions in antheridial filaments of Chara vulgaris

Within the proliferative period of spermatogenesis in <em>Chara vulgaris</em>, the progression throughout successive cell divisions in antheridial filaments is greatly influenced by changes in photoperiodic conditions. The extended (4-day) period of total darkness brings about cell cycle arrest in the early G2 phase. The recovery of mitosis requires about 20 hours of exposition to light. In the present study, a series of 8 pulse incubations of plants in cycloheximide (Cx; 2.5 mg/I, 2.5 h each pulse) were performed within the period elapsing till the resumption of mitotic divisions. Depending on the time of treatment, the effects induced by Cx vary considerably. Within the first 10 hs of exposition to light, incubations with Cx result in the delays of mitoses; within the period between the 10th and the 17th h, mitotic divisions become blocked, and, following the 17.5 h of light-induced recovery, no influence of Cx is noticed on mitotic activity, as compared with the untreaed control plants. The obtained results provide a starting point for the characteristic of proteins synthesized during the G2 phase and a preliminary study on those mechanisms, which become engaged in the regulation of the G1-deficient cell cycle evidenced in antheridial filaments of <em>Chara</em>.