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The stable carbon isotope composition of the carbonate encrustations ( delta super(13)C sub(CARB)) , organic matter ( delta super(13)C sub(ORG)) and the dissolved inorganic carbon ( delta super(13)C sub(DIC)) in the ambient lake waters were analysed for two common but morphologically different and, thus, representing different growth forms of Chara species. We hypothesized that the relationships between delta super(13)C sub(CARB), delta super(13)C sub(ORG) and delta super(13)C sub(DIC) are species specific and related to the different growth forms of the studied charophytes. For each species (Chara tomentosa and Chara globularis), 10 individuals and water samples from above the macrophytes were collected in five lakes at three sites per lake in mid-summer. Opposing shifts were found between delta super(13)C sub(CARB) and delta super(13)C sub(DIC) values with super(13)C enrichment in C. tomentosa and super(13)C depletion in C. globularis. In addition, C. globularis exhibited more negative values of delta super(13)C sub(ORG) than C. tomentosa, even under similar conditions. The delta super(13)C sub(CARB) and delta super(13)C sub(ORG) values were positively correlated in both species, but delta super(13)C sub(CARB) and delta super(13)C sub(DIC) as well as delta super(13)C sub(ORG) and delta super(13)C sub(DIC) were positively correlated in C. tomentosa only. The differences found result from the different proportions between super(13)C and super(12)C in DIC used as a CO sub(2) source for photosynthesis, which is linked to the different growth forms represented by the two studied charophytes and, thus, are species specific as we hypothesized.

Many cells exhibit large-scale active circulation of their entire fluid contents, a process termed cytoplasmic streaming. This phenomenon is particularly prevalent in plant cells, often presenting strikingly regimented flow patterns. The driving mechanism in such cells is known: myosin-coated organelles entrain cytoplasm as they process along actin filament bundles fixed at the periphery. Still unknown, however, is the developmental process that constructs the well-ordered actin configurations required for coherent cell-scale flow. Previous experimental works on streaming regeneration in cells of Characean algae, whose longitudinal flow is perhaps the most regimented of all, hint at an autonomous process of microfilament self-organization driving the formation of streaming patterns during morphogenesis. Working from first principles, we propose a robust model of streaming emergence that combines motor dynamics with both microscopic and macroscopic hydrodynamics to explain how several independent processes, each ineffectual on its own, can reinforce to ultimately develop the patterns of streaming observed in the Characeae and other streaming species.

BACKGROUND AND AIMS: The production of multicellular gametangia in green plants represents an early evolutionary development that is found today in all land plants and advanced clades of the Charophycean green algae. The processing of cell walls is an integral part of this morphogenesis yet very little is known about cell wall dynamics in early-divergent green plants such as the Charophycean green algae. This study represents a comprehensive analysis of antheridium development and spermatogenesis in the green alga, Chara corallina. METHODS: Microarrays of cell wall components and immunocytochemical methods were employed in order to analyse cell wall macromolecules during antheridium development. KEY RESULTS: Cellulose and pectic homogalacturonan epitopes were detected throughout all cell types of the developing antheridium including the unique cell wall protuberances of the shield cells and the cell walls of sperm cell initials. Arabinogalactan protein epitopes were distributed only in the epidermal shield cell layers and anti-xyloglucan antibody binding was only observed in the capitulum region that initially yields the sperm filaments. During the terminal stage of sperm development, no cell wall polymers recognized by the probes employed were found on the scale-covered sperm cells. CONCLUSIONS: Antheridium development in C. corallina is a rapid event that includes the production of cell walls that contain polymers similar to those found in land plants. While pectic and cellulosic epitopes are ubiquitous in the antheridium, the distribution of arabinogalactan protein and xyloglucan epitopes is restricted to specific zones. Spermatogenesis also includes a major switch in the production of extracellular matrix macromolecules from cell walls to scales, the latter being a primitive extracellular matrix characteristic of green plants.

Several Chara L. species have ‘unfinished’ morphogenesis that is recognizable because of their imperfect stem and branchlet cortication compared to the perfectly corticated species. Chara denudata A. Braun, described from South Africa, is one of these species, assumed for a long time to be conspecific with C. dissoluta A. Braun ex Leonhardi, as described from Central Europe. An attempt to resolve this long-lasting uncertainty in the framework of integrative taxonomy is implemented here. The restudy of the original material of both species showed similarities but did not identify a hiatus in their morphological traits, which represents evidence for their placement in the subsection Chara R.D. Wood according to morphology. Bifid adaxial bract cells, a trait rarely encountered among charophytes, were found for the first time in C. dissoluta. According to the rbcL and matK sequences, C. denudata was unexpectedly placed within the section Grovesia R.D. Wood, far from the clusters of the section Chara with C. dissoluta. This is in obvious disagreement with the position of C. denudata according to morphology. Both species were distinct according to their biology, habitat preference, and distribution and were accepted as distinct species. Therefore, the ‘unfinished’ morphogenesis resulting in morphological similarity hides different speciation pathways in charophytes.

Charophytes are a group of green algae that grow in various types of water ecosystems and are characterized by a high degree of plasticity and morphological variation. To analyze the genetic diversity and taxonomic rank of several species from the genus , the fingerprinting technique of Amplified Fragment Length Polymorphism (AFLP) was applied. We studied species that belong to sect. Grovesia ( , and and two species from the sect. Hartmania ( and . The individuals were collected in the field in north-eastern, central and eastern Poland. The species were identified based on morphological features and then analyzed using the AFLP fingerprinting method. UPGMA clustering and PCA analysis as well as morphological analysis revealed a clear separation of and , which formed separate clusters supported by high bootstrap values. Therefore, these species were distinguish as separate taxa, rather than varieties of . Similarly, also formed a separate cluster, thereby confirming that this taxon is a separate species, rather than a variety of . The AFLP analysis did not show any differentiation between and . The presented results do not fully support the taxonomic interpretation for the existence of several polymorphic species with numerous variations and forms, however, in some examples, the distinctive nature of the reproduction system may be used as a distinguishing feature of the taxa.

Metabolomics is the most reliable analytical method for understanding metabolic diversity in single organelles derived from single cells. Although metabolites such as phosphate compounds are believed to be localized in different organelles in a highly specific manner, the process of metabolite compartmentalization in the cell is not thoroughly understood. The analysis of metabolites in single organelles has consequently presented a significant challenge. In this study, we used a metabolomic method to elucidate the localization and dynamics of 125 known metabolites isolated from the vacuole and cytoplasm of a single cell of the alga Chara australis. The amount of metabolites in the vacuole and the cytoplasm fluctuated asynchronously under various stress conditions, suggesting that metabolites are spatially regulated within the cell. Metabolite transport across the vacuolar membrane can be directly detected using the microinjection technique, which may reveal a previously unknown function of the vacuole.

Linear alkylbenzene sulfonate (LAS) is a common organic pollutant in freshwater environments. Studies have shown that the toxicity of LAS to aquatic plants is directly related to the LAS concentration and depends on the plant species. A 2-week exposure experiment was designed to investigate the toxicity of LAS for the submerged plant Chara vulgaris L. and focused on the effects on growth, photosynthetic pigment content, and antioxidant enzyme activity. The results showed that when exposed to lower LAS doses (≤ 1.0 mg l−1), the dry weight of C. vulgaris was significantly reduced. Compared to those of the control group, superoxide dismutase (SOD) and peroxidase (POD) activities significantly increased, while no significant effect was observed for catalase (CAT) activity. Malondialdehyde (MDA) content significantly increased in the LAS treatment groups except for the LAS concentration of 1.0 mg l−1. The content of carotenoids was significantly lower in plant groups exposed to lower concentrations of LAS, while carotenoid content significantly increased at the highest concentration of LAS (5.0 mg l−1). LAS treatment did not significantly affect chlorophyll a and b or total chlorophyll content. The results showed that 5.0 mg l−1 causes some oxidative damage to C. vulgaris but that this concentration was far below the lethal concentration of LAS to C. vulgaris and did not produce severe effects on growth. C. vulgaris plants had some resistance to LAS stress (in the group with ≤ 5.0 mg l−1). SOD, POD, and carotenoids were more sensitive to the effects of LAS stress and may be considered as response indicators for LAS stress.

Our aim was to test the hypothesis that precipitation of calcite encrustation and accumulation of phosphorus by charophytes depend on both habitat conditions and plant species. To do this, we analysed the amount of calcite and phosphorus fractions in six charophyte species from ten lakes of different water chemistry. Percent of calcite encrustation in plant biomass was species specific— Chara rudis and Chara tomentosa produced most and Chara globularis and Chara intermedia least calcite. Lake water supersaturation with calcium carbonate was not necessary to induce calcite formation. Calcium and soluble phosphorus in lake water exerted significant (positive and negative, respectively) effect on calcite variability across species. Soluble and total phosphorus in lake water, however, were poor predictors of total phosphorus variability in plants. All plants accumulated more inorganic than organic phosphorus. Concentration of calcium-bound phosphorus per gram of calcite showed significant interspecific differences. Our data suggest that charophytes are capable of accumulating relatively large amounts of calcium carbonate and phosphorus (mostly calcium-bound P) in lake sediments.

Light is a fundamental driver of ecosystem dynamics, affecting the rate of photosynthesis and primary production. In spite of its importance, less is known about its community-scale effects on aquatic ecosystems compared with those of nutrient loading. Understanding light limitation is also important for ecosystem management, as human activities have been rapidly altering light availability to aquatic ecosystems. Here we show that decreasing light can paradoxically increase phytoplankton abundance in shallow lakes. Our results, based on field manipulation experiments, field observations and models, suggest that, under competition for light and nutrients between phytoplankton and submersed macrophytes, alternative stable states are possible under high-light supply. In a macrophyte-dominated state, as light decreases phytoplankton density increases, because macrophytes (which effectively compete for nutrients released from the sediment) are more severely affected by light reduction. Our results demonstrate how species interactions with spatial heterogeneity can cause an unexpected outcome in complex ecosystems. An implication of our findings is that partial surface shading for controlling harmful algal bloom may, counterintuitively, increase phytoplankton abundance by decreasing macrophytes. Therefore, to predict how shallow lake ecosystems respond to environmental perturbations, it is essential to consider effects of light on the interactions between pelagic and benthic producers.

Cytoplasmic streaming with extremely high velocity (∼70 μm s−1) occurs in cells of the characean algae (Chara). Because cytoplasmic streaming is caused by myosin XI, it has been suggested that a myosin XI with a velocity of 70 μm s−1, the fastest myosin measured so far, exists in Chara cells. However, the velocity of the previously cloned Chara corallina myosin XI (CcXI) was about 20 μm s−1, one-third of the cytoplasmic streaming velocity in Chara. Recently, the genome sequence of Chara braunii has been published, revealing that this alga has four myosin XI genes. We cloned these four myosin XI (CbXI-1, 2, 3, and 4) and measured their velocities. While the velocities of CbXI-3 and CbXI-4 motor domains (MDs) were similar to that of CcXI MD, the velocities of CbXI-1 and CbXI-2 MDs were 3.2 times and 2.8 times faster than that of CcXI MD, respectively. The velocity of chimeric CbXI-1, a functional, full-length CbXI-1 construct, was 60 μm s−1. These results suggest that CbXI-1 and CbXI-2 would be the main contributors to cytoplasmic streaming in Chara cells and show that these myosins are ultrafast myosins with a velocity 10 times faster than fast skeletal muscle myosins in animals. We also report an atomic structure (2.8-Å resolution) of myosin XI using X-ray crystallography. Based on this crystal structure and the recently published cryo-electron microscopy structure of acto-myosin XI at low resolution (4.3-Å), it appears that the actin-binding region contributes to the fast movement of Chara myosin XI. Mutation experiments of actin-binding surface loops support this hypothesis.