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Sexual reproduction in Charophyceae abounds in complex traits. Their gametangia develop as intricate structures, with oogonia spirally surrounded by envelope cells and richly pigmented antheridia. The red—probably protectant—pigmentation of antheridia is conserved across Charophyceae. Chara tomentosa is, however, unique in exhibiting this pigmentation and also in vegetative tissue. Here, we investigated the two sympatric species, C. tomentosa and Chara baltica, and compared their molecular chassis for pigmentation. Using reversed phase C30 high performance liquid chromatography (RP-C30-HPLC), we uncover that the major pigments are β-carotene, δ-carotene and γ-carotene; using headspace solid-phase microextraction coupled to gas chromatography equipped with a mass spectrometer (HS-SPME-GC-MS), we pinpoint that the unusually large carotenoid pool in C. tomentosa gives rise to diverse volatile apocarotenoids, including abundant 6-methyl-5-hepten-2-one. Based on transcriptome analyses, we uncover signatures of the unique biology of Charophycaee and genes for pigment production, including monocyclized carotenoids. The rich carotenoid pool probably serves as a substrate for diverse carotenoid-derived metabolites, signified not only by (i) the volatile apocarotenoids we detected but (ii) the high expression of a gene coding for a cytochrome P450 enzyme related to land plant proteins involved in the biosynthesis of carotenoid-derived hormones. Overall, our data shed light on a key protection strategy of sexual reproduction in the widespread group of macroalgae. The genetic underpinnings of this are shared across hundreds of millions of years of plant and algal evolution. This article is part of the theme issue 'The evolution of plant metabolism'. [ABSTRACT FROM AUTHOR]

In this contribution, new data concerning algae, bryophytes, fungi and lichens of the Italian flora are presented. It includes new records and confirmations for the algal genera Acetabularia, Nitella, and Nitellopsis for the bryophyte genera Drepanocladus, Fissidens, Hookeria, and Weissia, the fungal genera Alnicola, Arthonia, Cortinarius, Inocybe, Leucoagaricus, Neohygrocybe, and Puccinia and the lichen genera Bacidina, Chaenotheca, Flavoplaca, Gyalecta, Heterodermia, Rinodina, Scytinium, and Squamarina. [ABSTRACT FROM AUTHOR]

Nitella myriotricha A.Braun ex Kutzing ssp. acuminata SDu.bramanian 1999 has been recorded from different localities of West Bengal, eastern India. It is the first report of the taxon outside its original locality of occurrence at Kummidipoondi (Tamil Nadu) by Subramanian in 1999. The possibilities of endemism and origin of variations in this species have been discussed. [ABSTRACT FROM AUTHOR]

The article discusses the challenges of studying the biodiversity of algae and other protists. While these organisms are larger than bacteria and archaea, they still require microscopy for identification, and there are few structural characteristics that can be used for diagnosis. Metagenomic analysis, which has been successful for bacteria and archaea, is still developing for algae. The article focuses on the biodiversity of the Klebsormidiophyceae, a group of green algae, and highlights the difficulties in identifying species within this group. The study also explores the evolutionary history and genomic diversity of the Klebsormidiophyceae, revealing discrepancies between genetic and morphological evidence. The article emphasizes the importance of biodiversity discovery and the urgent need to study and describe novel or poorly known taxa before they are lost. [Extracted from the article]

Insights into the evolution of plant cell walls have important implications for comprehending these diverse and abundant biological structures. In order to understand the evolving structure-function relationships of the plant cell wall, it is imperative to trace the origin of its different components. The present study is focused on plant 1,4-β-xylan, tracing its evolutionary origin by genome and transcriptome mining followed by phylogenetic analysis, utilizing a large selection of plants and algae. It substantiates the findings by heterologous expression and biochemical characterization of a charophyte alga xylan synthase. Of the 12 known gene classes involved in 1,4-β-xylan formation, XYS1/IRX10 in plants, IRX7, IRX8, IRX9, IRX14 and GUX occurred for the first time in charophyte algae. An XYS1/IRX10 ortholog from Klebsormidium flaccidum, designated K. flaccidumXYLAN SYNTHASE-1 (KfXYS1), possesses 1,4-β-xylan synthase activity, and 1,4-β-xylan occurs in the K. flaccidum cell wall. These data suggest that plant 1,4-β-xylan originated in charophytes and shed light on the origin of one of the key cell wall innovations to occur in charophyte algae, facilitating terrestrialization and emergence of polysaccharide-based plant cell walls.

For studying land plant evolution, the establishment and optimization of model organisms representing streptophytic algae, sister to land plants, is essential. Long-term cultivation experiments with Chara braunii S276 were performed over 8 years, since 4 years (Nov. 2018) under constant conditions. Additionally, short-term experiments for optimization of culture conditions were performed with three strains of C. braunii (S276, NIES-1604 and Lausiger Teiche, LaT-2708). Germination success after application of sterilization agents, addition of gibberellic acid and under different incubation conditions with respect to pretreatment, irradiance regime and substrate was investigated in order to develop protocols for generative cultivation of at least unialgal cultures. The resulting cultivation protocols for C. braunii S276, allowing maintenance of vegetative as well as generative cultures are presented in detail, including protocols for germination induction and growth of sterilized and unsterilized oospores. [ABSTRACT FROM AUTHOR]

BackgroundStrigolactones (SLs) are a class of plant hormones that control many aspects of plant growth. The SL signalling mechanism is homologous to that of karrikins (KARs), smoke-derived compounds that stimulate seed germination. In angiosperms, the SL receptor is an α/β-hydrolase known as DWARF14 (D14); its close homologue, KARRIKIN INSENSITIVE2 (KAI2), functions as a KAR receptor and likely recognizes an uncharacterized, endogenous signal ('KL'). Previous phylogenetic analyses have suggested that the KAI2 lineage is ancestral in land plants, and that canonical D14-type SL receptors only arose in seed plants; this is paradoxical, however, as non-vascular plants synthesize and respond to SLs.ResultsWe have used a combination of phylogenetic and structural approaches to re-assess the evolution of the D14/KAI2 family in land plants. We analysed 339 members of the D14/KAI2 family from land plants and charophyte algae. Our phylogenetic analyses show that the divergence between the eu-KAI2 lineage and the DDK (D14/DLK2/KAI2) lineage that includes D14 occurred very early in land plant evolution. We show that eu-KAI2 proteins are highly conserved, and have unique features not found in DDK proteins. Conversely, we show that DDK proteins show considerable sequence and structural variation to each other, and lack clearly definable characteristics. We use homology modelling to show that the earliest members of the DDK lineage structurally resemble KAI2 and that SL receptors in non-seed plants likely do not have D14-like structure. We also show that certain groups of DDK proteins lack the otherwise conserved MORE AXILLARY GROWTH2 (MAX2) interface, and may thus function independently of MAX2, which we show is highly conserved throughout land plant evolution.ConclusionsOur results suggest that D14-like structure is not required for SL perception, and that SL perception has relatively relaxed structural requirements compared to KAI2-mediated signalling. We suggest that SL perception gradually evolved by neo-functionalization within the DDK lineage, and that the transition from KAI2-like to D14-like protein may have been driven by interactions with protein partners, rather than being required for SL perception per se.

For studying land plant evolution, the establishment and optimization of model organisms representing streptophytic algae, sister to land plants, is essential. Long-term cultivation experiments with Chara braunii S276 were performed over 8 years, since 4 years (Nov. 2018) under constant conditions. Additionally, short-term experiments for optimization of culture conditions were performed with three strains of C. braunii (S276, NIES-1604 and Lausiger Teiche, LaT-2708). Germination success after application of sterilization agents, addition of gibberellic acid and under different incubation conditions with respect to pre-treatment, irradiance regime and substrate was investigated in order to develop protocols for generative cultivation of at least unialgal cultures. The resulting cultivation protocols for C. braunii S276, allowing maintenance of vegetative as well as generative cultures are presented in detail, including protocols for germination induction and growth of sterilized and unsterilized oospores.

In this contribution, new data concerning bryophytes, fungi and lichens of the Italian flora are presented. It includes new records and confirmations for the algal genus Chara, for the bryophyte genera Bryum, Grimmia, Cephaloziella, Hypnum, Nogopterium, Physcomitrium, Polytrichastrum, Rhynchostegiella, Saelania, and Schistostega, the fungal genera Cortinarius, Lentinellus, Omphalina, and Xerophorus, and the lichen genera Acarospora, Agonimia, Candelariella, Cladonia, Graphis, Gyalolechia, Hypogymnia, Lichinella, Megalaria, Nephroma, Ochrolechia, Opegrapha, Peltigera, Placidium, Ramalina, Rhizoplaca, Ropalospora, Strangospora, Toniniopsis, Usnea, and Zahlbrucknerella. [ABSTRACT FROM AUTHOR]

Members of the brackish-water species Lamprothamnium succinctum (Charales, Charophyceae) are widely distributed from tropical to temperate regions, including East Asia. In Japan, L. succinctum is listed as an endangered species and is protected by the government, because it was recorded only at two localities, Lake Hachiro-gata (Akita Prefecture) and Oo-ike pond (Deba-jima Island, Tokushima prefecture), and has become extinct in the former. In this study, we identified five new localities of this species in Japan. The morphological characteristics of their thalli agreed with those provided in the original description of this species, with distinctive reproductive characteristics. Moreover, the oospores of Japanese specimens of L. succinctum were examined for the first time using scanning electron microscopy. The oospores of Japanese specimens exhibited granulate fossa wall patterns, which were consistent with those described in previous studies. Our genetic analyses based on the DNA sequences of two chloroplast DNA markers, including both the coding and non-coding regions, revealed that the sample from Oo-ike pond is distinguishable from those from other Japanese specimens, although they are genetically very similar.

SUMMARY: Charophyte green algae (CGA) are assigned to be the closest relatives of land plants and therefore enlighten processes in the colonization of terrestrial habitats. For the transition from water to land, plants needed significant physiological and structural changes, as well as with regard to cell wall composition. Sequential extraction of cell walls of Nitellopsis obtusa (Charophyceae) and Spirogyra pratensis (Zygnematophyceae) offered a comparative overview on cell wall composition of late branching CGA. Because arabinogalactan‐proteins (AGPs) are considered common for all land plant cell walls, we were interested in whether these special glycoproteins are present in CGA. Therefore, we investigated both species with regard to characteristic features of AGPs. In the cell wall of Nitellopsis, no hydroxyproline was present and no AGP was precipitable with the β‐glucosyl Yariv's reagent (βGlcY). By contrast, βGlcY precipitation of the water‐soluble cell wall fraction of Spirogyra yielded a glycoprotein fraction rich in hydroxyproline, indicating the presence of AGPs. Putative AGPs in the cell walls of non‐conjugating Spirogyra filaments, especially in the area of transverse walls, were detected by staining with βGlcY. Labelling increased strongly in generative growth stages, especially during zygospore development. Investigations of the fine structure of the glycan part of βGlcY‐precipitated molecules revealed that the galactan backbone resembled that of AGPs with 1,3‐ 1,6‐ and 1,3,6‐linked Galp moieties. Araf was present only in small amounts and the terminating sugars consisted predominantly of pyranosidic terminal and 1,3‐linked rhamnose residues. We introduce the term 'rhamnogalactan‐protein' for this special AGP‐modification present in S. pratensis. [ABSTRACT FROM AUTHOR]

Phytochromes are red/far-red photoreceptors that play essential roles in diverse plant morphogenetic and physiological responses to light. Despite their functional significance, phytochrome diversity and evolution across photosynthetic eukaryotes remain poorly understood. Using newly available transcriptomic and genomic data we show that canonical plant phytochromes originated in a common ancestor of streptophytes (charophyte algae and land plants). Phytochromes in charophyte algae are structurally diverse, including canonical and non-canonical forms, whereas in land plants, phytochrome structure is highly conserved. Liverworts, hornworts and Selaginella apparently possess a single phytochrome, whereas independent gene duplications occurred within mosses, lycopods, ferns and seed plants, leading to diverse phytochrome families in these clades. Surprisingly, the phytochrome portions of algal and land plant neochromes, a chimera of phytochrome and phototropin, appear to share a common origin. Our results reveal novel phytochrome clades and establish the basis for understanding phytochrome functional evolution in land plants and their algal relatives.

This study examined the rheological properties of alginates, one of the main products obtained from algae. These polysaccharides are widely used in fields such as pharmaceuticals, medical technology, cosmetics, food, agriculture and the textile and paper industries. Therefore, sodium alginate was obtained from waterweed (Charophyceae) in the following experiment. The structure and composition of the sodium alginate were analyzed using physical and chemical research methods: IR spectroscopy and XRD.

IntroductionWe evaluated periphytic algal and microbial communities to assess the influence of human and cattle impact on Sierra water quality.Methods64 sites (lakes and streams from Lake Tahoe to Sequoia National Park, California) were sampled for suspended indicator bacteria and algae following standardized procedures. The potential for nonpoint pollution was divided into three categories: cattle-grazing areas (C), recreation use areas (R), or remote wildlife areas (W).ResultsPeriphyton was found at 100% of C sites, 89% of R sites, but only 25% of W sites. Eleven species of periphytic algae were identified, including Zygnema, Ulothrix, Chlorella, Spirogyra, mixed Diatoms, and Cladophoria. Mean benthic algae coverage was 66% at C sites compared to 2% at W sites (P < 0.05). The prevalence of E. coli associated with periphyton was 100% at C sites, 25% of R sites, and 0% of W sites. Mean E. coli CFU/gm of algae detected was: C = 173,000, R = 700, W = 0. (P < 0.05). Analysis of neighboring water for E. coli bacteria >100 CFU/100 mL: C = 91%, R = 8%, W = 0 (P < 0.05).ConclusionHigher periphytic algal biomass and uniform presence of periphyton-attached E. coli corresponded to watersheds exposed to summer cattle grazing. These differences suggest cattle grazing compromises water quality.

Stoneworts (Charales) are green algae that represent an important food resource for many waterbird species in Europe and elsewhere. Browsing avian herbivores (e.g. swan, goose, duck and coot species) consume Charales plant vegetative parts, by head-dipping, up-ending or diving. A lower fibre content and longer growing season may make Charales as attractive to such herbivores as sympatric submerged higher plant species in some circumstances. Charales respond to environmental stress (e.g. drought) by producing abundant diaspores, in the form of oospores (sexual) and bulbils (asexual), both rich in starch, generating abundant food for waterbirds at critical stages in their annual migratory cycles. Waterbirds feed on these by diving (e.g. common pochard Aythya ferina and red-crested pochard Netta rufina) or by filtering from the water column (e.g. dabbling duck species), ensuring dispersal of sexually produced and vegetative diaspores locally (because of predator swamping) and remotely (through endo- and ectozoochorous dispersal by long-distance migratory waterbirds). Greater invertebrate density and diversity associated with Charales canopies enhances their attractiveness over other submerged macrophyte beds to diving predators [e.g. tufted duck Aythya fuligula, common pochard and Eurasian coot Fulica atra (hereafter coot)]. Fish fry preying on these invertebrates use such vegetation as predator cover, in turn providing prey for avian piscivores such as grebes and cormorants. Abundant Charales contribute to maintaining a transparent water column due to canopy density, nutrient effects, dampening of sedimentation/remobilisation of suspended matter and nutrients and allelopathic effects on other plants (especially phytoplankton). Shallow, relatively eutrophic waters can flip between clear-water high-biodiversity (where Charales thrive) and turbid species-poor depauperate stable states (lacking Charales). Shifts between turbid conditions and rich submerged Charales beds have profound elevating effects on aquatic diversity, to which waterbirds show rapid aggregative responses, making them ideal indicator species of ecological change; in the case of Charales specialists (such as red-crested and common pochard), indicators of the presence and abundance of these plants. Large-bodied colonial nesting birds (e.g. cormorants, gulls, heron and egrets) aggregating along lake shores contribute high N and P loadings to water bodies sensitive to such external and internal inputs and can cause local eutrophication and potential loss of Charales. Despite variation from complete seasonal removal of Charales biomass to undetectable grazing effects by herbivorous birds, evidence suggests little effect of avian grazing on biomass accumulation or the stability of community composition (under otherwise stable conditions), but we urge more research on this under-researched topic. We also lack investigations of the relative foraging profitability of different Charales organs to waterbirds and the degree of viability of gyrogonites (fertilised and calcified oospores), vegetative bulbils and plant fragments after passage through the guts of waterbirds. We especially need to understand better how much the carbonate armour of these organs affects their viability/dispersal via waterbirds and urge more research on these neglected plants and their relationships and interactions with other organisms in the aquatic biota., (© 2023 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.)

To date (1 November 2023), the online database AlgaeBase has documented 50,589 species of living algae and 10,556 fossil species here referred to four kingdoms (Eubacteria, Chromista, Plantae, and Protozoa), 14 phyla, and 63 classes. The algae are the third most speciose grouping of plant-like organisms after the flowering plants (≈382,000 species) and fungi (≈170,000 species, including lichens) but are the least well defined of all the botanical groupings. Priority is given to phyla and class names that are familiar to phycologists and that are nomenclaturally valid. The most species-rich phylum is the Heterokontophyta to which 18 classes are referred with 21,052 living species and which is dominated by the diatoms in three classes with 18,673 species (16,427 living; 2239 fossil). The next most species-rich phyla are the red algae (7276 living), the green algae (6851 living), the blue-green algae (Cyanobacteria, 5723 living), the charophytes (4950 living, including the Charophyceae, 511 species living, and the Zygnematophyceae, 4335 living species), Dinoflagellata (2956 living, including the Dinophyceae, 2828 extant), and haptophytes (Haptophyta 1722 species, 517 living)., (© 2024 The Authors. Journal of Phycology published by Wiley Periodicals LLC on behalf of Phycological Society of America.)

A relatively neglected element of the biota of the Lower Devonian Rhynie chert Lagerstätte are filamentous green algae exceptionally preserved by silicification. Palynological processing of sediments associated with the cherts has yielded palynomorphs that we also interpret as the remains of filamentous green algae and one such taxon is described herein. Cells occur individually, in masses or joined end-to-end as an unbranched filament. The cells are characterised by end walls that form a 'collar' structure and inner bodies interpreted as reproductive structures. Because of a lack of preserved characters taxonomic precision is limited, although we suggest the fossils are most likely either zygnematalean or oedogonialean algae that inhabited ponds or lakes and were either attached to substrates and/or free-floating. [ABSTRACT FROM AUTHOR]

In this contribution, new data concerning algae, bryophytes, fungi, and lichens of the Italian flora are presented. It includes new records and confirmations for the algae genus Chara, the bryophyte genera Homalia, Mannia, and Tortella, the fungal genera Cortinarius, Russula, and Stereum, and the lichen genera Cetrelia, Cladonia, Enterographa, Graphis, Lecanora, Lepraria, Multiclavula, Mycomicrothelia, Parmelia, Peltigera, Pleopsidium, Psora, Scytinium, Umbilicaria, and Rhizocarpon. [ABSTRACT FROM AUTHOR]

Increases in ultraviolet radiation (UVR), a negative global change factor, affect aquatic primary producers. This effect is expected to be modulated by other global change factors, and to be different for populations adapted to different environments. A common garden experimental approach using freshwater green macroalgae, the cosmopolitan charophyte species Chara hispida and C. vulgaris, allowed us to test whether the beneficial increases in water temperature (T) and nitrate concentration (N) mitigate negative UVR effects. Also, whether these interactions would be not only species--specific but also according to the origin of the population; therefore, two populations of each species were used: one from a coastal wetland and the other from a mountain lake. Two factorial-design experiments were performed: (i) the presence and absence of UVR 3 lower and higher T 3 four populations, and (ii) the presence and absence of UVR 3 lower and higher N 3 four populations. Response variables were: growth, morphometry, UVR-protective compounds, photosynthetic pigments, and stoichiometric composition. There were consistent response patterns in the key variables that represent different organization levels. Our main results showed that both warming and, to a lesser extent, the increase in nutrients ameliorated the negative effects of UVR on the molecular processes involved in acclimation to UVR, and that such a mitigating effect depended on the different phenotypic plasticity of each species and each ecotype. The coastal populations, being from a more variable environment, were more resilient than the mountain populations, mainly because of changes in growth and morphology. [ABSTRACT FROM AUTHOR]

The diaspore banks from two brackish ponds within the Albufera de València Natural Park (Spain) containing oospores of Chara hispida, C. aspera, C. canescens and Nitella hyalina were analysed and their germination capability studied under controlled temperature conditions. The top layer of sediment from each meadow was collected and sequentially sieved to isolate the charophyte oospores, subsequently identified and counted under the microscope. The density of apparently viable fructifications varied largely within the studied ponds and within specific meadows. In general, but not always, the most abundant oospores belonged to the species forming the meadow. An additional set of surficial sediment samples were collected to perform germination trials in an indoor culture room under three temperature treatments (21, 25 and 29°C). For each species, 219–272 fructifications were allocated inside small perforated packages that were placed in Petri dishes (n = 3) and submerged for 40 days in plastic containers. Germination rates were low for the four species in all temperatures (0–7%), with no large differences detected amongst treatments. C. aspera was the first species to germinate and the one with the most germlings. Higher temperatures negatively affected its germination; the same trend was shown by C. canescens. Dense oospore banks and low germination rates have been previously described for charophytes from temporary habitats. However, it seems that the recovery of charophyte meadows after droughts will be hindered by a warmer climate. Further studies concerning the optimal conditions for germination are needed to understand the future capability of charophyte meadows to re-establish in Mediterranean ecosystems. [ABSTRACT FROM AUTHOR]

To efficiently detect aquatic invasive species early in an invasion when control may still be possible, predictions about which locations are likeliest to be occupied are needed at fine scales but are rarely available. Occupancy modeling could provide such predictions given data of sufficient quality and quantity. We assembled a data set for the macroalga starry stonewort (Nitellopsis obtusa) across Minnesota and Wisconsin, USA, where it is a new and high-priority invader. We used these data to construct a multi-season, single-species spatial occupancy model that included biotic, abiotic, and movement-related predictors. Distance to the nearest access was an important occurrence predictor, highlighting the likely role boats play in spreading starry stonewort. Fetch and water depth also predicted occupancy. We estimated an average detection probability of 63% at sites with mean non-N. obtusa plant cover, declining to ~ 38% at sites with abundant plant cover, especially that of other Characeae. We recommend that surveyors preferentially search for starry stonewort in areas of shallow depth and high fetch close to boat accesses. We also recommend searching during late summer/early fall when detection is likelier. This study illustrates the utility of fine-scale occupancy modeling for predicting the locations of nascent populations of difficult-to-detect species., (© 2024. The Author(s).)

In this contribution, new data concerning algae, bryophytes, fungi, and lichens of the Italian flora are presented. It includes new records and confirmations for the algae genus Chara, the bryophyte genera Cephalozia, Conardia, Conocephalum, Didymodon, Sphagnum, Tetraplodon, and Tortula, the fungal genera Endophyllum, Gymnosporangium, Microbotryum, Phragmidium, and Pluteus, and the lichen genera Candelariella, Cladonia, Flavoplaca, Lichenothelia, Peltigera, Placolecis, Rinodina, Scytinium, and Solenopsora. [ABSTRACT FROM AUTHOR]

Chara dominii Vilh. is a new species in the flora in Russia. It has been found in Altai krai, Astrakhan oblast, and the Republic of Kalmykia. These findings change the concept of the northern border of the species living range considerably, as practically all C. dominii finds reported up to now were made in Central Asia. A description of the samples under study is given, and the living range of the species is characterized. [ABSTRACT FROM AUTHOR]

To clarify species diversity of Tolypella (Characeae, Charophyceae) and the relationship between Tolypella and other genera in Characeae, sequence data from the nuclear ribosomal operon were assembled for 18 individuals of Tolypella. These represented nine named species and two potentially new species from Australia, as well as 13 other taxa of Characeae. Phylogenetic analyses were performed on ribosomal gene sequences (18S, 5.8S and 28S) for Characeae and on ribosomal gene and internal transcribed spacer (ITS) sequences (ribosomal genes + ITS1 + ITS2) for Tolypella. Analyses were also performed on the ribosomal gene and ITS sequences combined with plastid gene sequences ( atpB, psbC and rbcL). Ribosomal gene sequences alone were conservative and their phylogenetic analyses resulted in topologies similar to a previously published plastid gene-based study but with less support and resolution. In contrast, ITS sequences showed greater variability and their addition resulted in greater resolution among some species relationships of Tolypella. The addition of plastid sequences also resulted in greater support and increased resolution in some lineages but not all. [ABSTRACT FROM AUTHOR]

The distribution data of 11 soft substrate charophyte and angiosperm species were analyzed. Our study aimed to elucidate the co-occurrence patterns among these sympatric macrophyte species and quantify their distribution areas. The central hypothesis of this study proposed that the observed co-occurrence patterns among the studied species deviate from what would be expected by random chance. Macrophyte occurrence data was derived from an extensive field sampling database. Environmental variables available as georeferenced raster layers including topographical, hydrodynamic, geological, physical, chemical, and biological variables were used as predictor variables in the random forest models to predict the spatial distribution of the species. Permutation tests revealed statistically significant deviations from random co-occurrence patterns. The analysis demonstrated that species tended to co-occur more frequently within their taxonomic groups (i.e., within charophytes and within angiosperms) than between these groups. The most extensive distribution overlap was observed between Chara aspera Willd. and Chara canescens Loisel., while Zostera marina L. exhibited the least overlap with the other species. The mean number of co-occurring species was the highest in Chara baltica (Hartman) Bruzelius while Z. marina had the largest share of single-species occurrences. Based on the distribution models, Stuckenia pectinata (L.) Börner had the largest distribution area., (© 2023. The Author(s).)

The Viridiplantae comprise two main clades, the Chlorophyta (including a diverse array of marine and freshwater green algae) and the Streptophyta (consisting of the freshwater charophytes and the land plants). Lineages sister to core Chlorophyta, informally refer to as prasinophytes, form a grade of mainly planktonic green algae. Recently, one of these lineages, Prasinodermophyta, which is previously grouped with prasinophytes, has been identified as the sister lineage to both Chlorophyta and Streptophyta. Resolving the deep relationships among green plants is crucial for understanding the historical impact of green algal diversity on marine ecology and geochemistry, but has been proven difficult given the ancient timing of the diversification events. Through extensive taxon and gene sampling, we conduct large-scale phylogenomic analyses to resolve deep relationships and reveal the Prasinodermophyta as the lineage sister to Chlorophyta, raising questions about the necessity of classifying the Prasinodermophyta as a distinct phylum. We unveil that incomplete lineage sorting is the main cause of discordance regarding the placement of Prasinodermophyta. Molecular dating analyses suggest that crown-group green plants and crown-group Prasinodermophyta date back to the Paleoproterozoic-Mesoproterozoic. Our study establishes a plausible link between oxygen levels in the Paleoproterozoic-Mesoproterozoic and the origin of Viridiplantae., (© 2023. Springer Nature Limited.)

Background and Aims: Endosidins are a group of low-molecular-weight compounds, first identified by 'chemical biology' screening assays, that have been used to target specific components of the endomembrane system. In this study, we employed multiple microscopy-based screening techniques to elucidate the effects of endosidin 5 (ES5) on the Golgi apparatus and the secretion of extracellular matrix (ECM) components in Penium margaritaceum. These effects were compared with those caused by treatments with brefeldin A and concanamycin A. Penium margaritaceum's extensive Golgi apparatus and endomembrane system make it an outstanding model organism for screening changes to the endomembrane system. Here we detail changes to the Golgi apparatus and secretion of ECM material caused by ES5., Methods: Changes to extracellular polymeric substance (EPS) secretion and cell wall expansion were screened using fluorescence microscopy. Confocal laser scanning microscopy and transmission electron microscopy were used to assess changes to the Golgi apparatus, the cell wall and the vesicular network. Electron tomography was also performed to detail the changes to the Golgi apparatus., Key Results: While other endosidins were able to impact EPS secretion and cell wall expansion, only ES5 completely inhibited EPS secretion and cell wall expansion over 24 h. Short treatments of ES5 resulted in displacement of the Golgi bodies from their typical linear alignment. The number of cisternae decreased per Golgi stack and trans face cisternae in-curled to form distinct elongate circular profiles. Longer treatment resulted in a transformation of the Golgi body to an irregular aggregate of cisternae. These alterations could be reversed by removal of ES5 and returning cells to culture., Conclusions: ES5 alters secretion of ECM material in Penium by affecting the Golgi apparatus and does so in a markedly different way from other endomembrane inhibitors such as brefeldin A and concanamycin A., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Annals of Botany Company.)

The streptophyte green algal class Zygnematophyceae is the immediate sister lineage to land plants. Their special form of sexual reproduction via conjugation might have played a key role during terrestrialization. Thus, studying Zygnematophyceae and conjugation is crucial for understanding the conquest of land. Moreover, sexual reproduction features are important for species determination. We present a phylogenetic analysis of a field-sampled Zygnema strain and analyze its conjugation process and zygospore morphology, both at the micro- and nanoscale, including 3D-reconstructions of the zygospore architecture. Vegetative filament size (26.18 ± 1.07 μm) and reproductive features allowed morphological determination of Zygnema vaginatum, which was combined with molecular analyses based on rbcL sequencing. Transmission electron microscopy (TEM) depicted a thin cell wall in young zygospores, while mature cells exhibited a tripartite wall, including a massive and sculptured mesospore. During development, cytological reorganizations were visualized by focused ion beam scanning electron microscopy (FIB-SEM). Pyrenoids were reorganized, and the gyroid cubic central thylakoid membranes, as well as the surrounding starch granules, degraded (starch granule volume: 3.58 ± 2.35 μm 3 in young cells; 0.68 ± 0.74 μm 3 at an intermediate stage of zygospore maturation). Additionally, lipid droplets (LDs) changed drastically in shape and abundance during zygospore maturation (LD/cell volume: 11.77% in young cells; 8.79% in intermediate cells, 19.45% in old cells). In summary, we provide the first TEM images and 3D-reconstructions of Zygnema zygospores, giving insights into the physiological processes involved in their maturation. These observations help to understand mechanisms that facilitated the transition from water to land in Zygnematophyceae., (© 2023 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)

Harriman and Bear Mountain State Parks, New York, contain a rich and previously under-documented algal flora. We report 382 algal taxa (excluding diatoms), including 294 taxa not previously reported from the parks. Our inventory suggests that the algal flora has changed significantly since it was last studied in 1918 with a general increase in the number of desmid taxa (Zygnematophyceae) and changes in the species composition of other green algae. We hypothesize that these changes are primarily due to normal succession in constructed lakes. Some of the species encountered are infrequently reported from North America. Consequently Harriman and Bear Mountain State Parks represents an important locality for their study. Factors possibly contributing to the apparent rarity of species are discussed. A new species of Dinobryon (Chrysophyceae: Dinobryaceae) is described: Dinobryon sertularioides. Two new taxonomic combinations are also made: Stauridium tetras var. tetraodon (Chlorophyceae: Hydrodictyaceae) and Cosmarium verrucosum var. alatum (Zygnematophyceae: Desmidiaceae) . [ABSTRACT FROM AUTHOR]

Temporal and spatial variation of Nitella furcata (Roxburgh ex Bruzelius) C. Agardh emend. R.D. Wood subsp. mucronata (A. Braun) R.D. Wood var. mucronata f. oligospira (A. Braun) R.D. Wood were studied at the Ninféias pond (23°38'18.9"S, 46°37'16.3"W), a tropical, shallow, mesotrophic reservoir located in the Parque Estadual das Fontes do Ipiranga Biological Reserve, Municipality of São Paulo, southeast Brazil. Water samples were collected monthly from October/1996 to October/1997 for turbidity, electric conductivity, pH, alkalinity, dissolved oxygen, nutrients, biomass, and algal phenology analysis. Spatial distribution pattern of algal biomass showed that all four sampling stations were similar among themselves during the whole study period. Regarding the temporal variation, greatest algal total biomass values (98.35-266.06 g.m-2) were measured during the rainy period whereas the smallest ones (48.86-170.56 g.m-2) were detected during the dry period. Algal population density peaked at all four sampling stations from October/1996 to April/1997 (rainy period) when the greatest values of air and water temperature, precipitation, solar radiation, turbidity, total nitrogen, and ammonium were measured allowing favorable conditions for the algal growth. Period from May/1997 (late fall) to October/1997 (early spring) was favorable to the development of reproductive structures (nucules and globules) with consequent decrease of algal biomass and population density, clearly suggesting the greatest energy allocation towards the development of sexual reproductive structures. This fact was confirmed by the canonic correspondence analysis that indicated strong correlation between nucules length and width, number of nucules per plant, and oospores length and width with the low values of pH and high ones of dissolved inorganic matter detected during the dry period. Consequently, environmental factors such as increasing of water temperature and nutrients availability at the Ninféias pond acted decisively towards growth and accumulation of algal biomass.Dinâmica temporal de uma população de Nitella furcata (Roxburgh ex Bruzelius) C. Agardh emend. R.D. Wood subsp. mucronata (A. Braun) R.D. Wood var. mucronata f. oligospira (A. Braun) R.D. Wood foi estudada no Lago das Ninféias (23°38'18,9"S, 46°37'16,3"W), um reservatório tropical, raso, mesotrófico situado na Reserva Biológica do Parque Estadual das Fontes do Ipiranga, Município de São Paulo, sudeste do Brasil. Amostras de água foram coletadas mensalmente de outubro/1996 a outubro/1997 para análise de turbidez, condutividade elétrica, pH, alcalinidade, oxigênio dissolvido, nutrientes, biomassa e fenologia da alga. Os maiores valores médios de biomassa total da carácea (98,35-266,06 g.m-2) foram registrados no período de chuvas e os menores (48,86-170,56 g.m-2) no seco. A densidade populacional apresentou picos de outubro/1996 a abril/1997, isto é, durante a estação chuvosa, época em que foram registrados os maiores valores de temperatura do ar e da água, de precipitação pluvial, radiação solar, turbidez, nitrogênio total e de amônio, constituindo condições favoráveis para o crescimento das plantas. O período entre maio/1997 (final do outono) e outubro/1997 (início da primavera) mostrou-se favorável ao desenvolvimento de estruturas reprodutivas (núculas e glóbulos), com diminuição de biomassa e densidade populacional da carácea, sugerindo maior alocação de energia para a formação de estruturas reprodutivas. Este fato foi confirmado pela análise de correspondência canônica, que registrou fortes correlações entre comprimento e diâmetro das núculas, número total de núculas por planta e comprimento e diâmetro dos oósporos, com os baixos valores de pH e altos de matéria orgânica verificados no período de seca. Concluindo, fatores ambientais, como aumento de temperatura da água e disponibilidade de nutrientes, parecem exercer influência decisiva sobre o crescimento e acúmulo de biomassa da alga no Lago das Ninféias.

The taxonomic status of Nitella flexilis var. bifurcata (Charales, Characeae), which is endemic to Japan, has remained unclear because there have been no records since its description in 1964, and the detailed morphology of fully mature individuals as well as its molecular phylogeny have not been studied. Recently, we collected a fully mature N. flexilis var. bifurcata from two lakes near the type locality in Japan. The morphological characteristics of the thalli agreed well with that in the original description of the taxon, with distinctive fertile and sterile branchlets that divided twice and unicellular dactyls. Scanning electron microscopy showed that the fine oospore structure of N. flexilis var. bifurcata was different from that of related taxa. In addition, molecular phylogenetic and haplotype network analyses using the chloroplast rbcL DNA sequences and the intergenic spacer regions between atpB and rbcL genes demonstrated that N. flexilis var. bifurcata and N. flexilis var. flexilis were distinct. [ABSTRACT FROM AUTHOR]

The charophytic green alga Nitellopsis obtusa was first reported in the New World in the St. Lawrence River in 1978. Since that time, N. obtusa has been reported from inland lakes throughout Michigan, northern Indiana, and western New York and has been listed as an aggressive invasive species by the United States Geological Survey. This study addresses the distribution of N. obtusa by surveying 390 waterbodies throughout New York. Previous reports are confirmed and new localities are presented, including new reports from five counties (Franklin, Ontario, Seneca, Wayne, and Yates). In total, N. obtusa was found in 17 counties at 31 sites, including 16 inland lakes, seven sites in the St. Lawrence River, and eight sites in Lake Ontario. [ABSTRACT FROM AUTHOR]

Characeae ( Charophyceae, Charophyta) contains two tribes with six genera: tribe Chareae with four genera and tribe Nitelleae, which includes Tolypella and Nitella. This paper uses molecular and morphological data to elucidate the phylogeny of Tolypella species in North America. In the most comprehensive taxonomic treatment of Characeae, 16 Tolypella species worldwide were subsumed into two species, T. intricata and T. nidifica, in two sections, Rothia and Tolypella respectively. It was further suggested that Tolypella might be a derived group within Nitella. In this investigation into species diversity and relationships in North American Tolypella, sequence data from the plastid genes atpB, psbC, and rbcL were assembled for a broad range of charophycean and land plant taxa. Molecular data were used in conjunction with morphology to test monophyly of the genus and species within it. Phylogenetic analyses of the sequence data showed that Characeae is monophyletic but that Nitelleae is paraphyletic with Tolypella sister to a monophyletic Nitella + Chareae. The results also supported the monophyly of Tolypella and the sections Rothia and Tolypella. Morphologically defined species were supported as clades with little or no DNA sequence differences. In addition, molecular data revealed several lineages and a new species ( T. ramosissima sp. nov.), which suggests greater species diversity in Tolypella than previously recognized. [ABSTRACT FROM AUTHOR]

Chara braunii is distributed worldwide and is the most common charalean species in Japan. This species is monoecious and produces numerous sets of sex organs, each of which consists of one antheridium and one oogonium, under laboratory culture conditions. In this study, we report that light intensity strongly affected the vegetative phase and sexual reproductive phase of this species. Under high-light conditions (70.0 μmol photons m−2 s−1), thalli grew but did not form reproductive organs. Under a low-light intensity (10.0 μmol photons m−2 s−1), algal bodies formed many reproductive organs. In addition, antheridia without the corresponding oogonia (lone antheridia) were observed under low-light conditions. The absence of oogonium primordia adjacent to the lone antheridium was confirmed by several microscopic approaches. The addition of liquid fertilizer increased the total number of sex organs and growth; however, the number of lone antheridia decreased with increasing fertilizer concentrations. Exogenously applied gibberellin did not affect the number of lone antheridia. These results suggest that regulatory mechanisms for the appropriate allocation of resources exist in this alga, similar to those reported in some land plants. [ABSTRACT FROM AUTHOR]

Six monophyletic groups of charophycean green algae are recognized within the Streptophyta. Although incongruent with earlier studies based on genes from three cellular compartments, chloroplast and nuclear phylogenomic analyses have resolved identical relationships among these groups, placing the Zygnematales or the Zygnematales + Coleochaetales as sister to land plants. The present investigation aimed at determining whether this consensus view is supported by the mitochondrial genome and at gaining insight into mitochondrial DNA (mtDNA) evolution within and across streptophyte algal lineages and during the transition toward the first land plants. We present here the newly sequenced mtDNAs of representatives of the Klebsormidiales (Entransia fimbriata and Klebsormidium spec.) and Zygnematales (Closterium baillyanum and Roya obtusa) and compare them with their homologs in other charophycean lineages as well as in selected embryophyte and chlorophyte lineages. Our results indicate that important changes occurred at the levels of genome size, gene order, and intron content within the Zygnematales. Although the representatives of the Klebsormidiales display more similarity in genome size and intron content, gene order seems more fluid and gene losses more frequent than in other charophycean lineages. In contrast, the two members of the Charales display an extremely conservative pattern of mtDNA evolution. Collectively, our analyses of gene order and gene content and the phylogenies we inferred from 40 mtDNA-encoded proteins failed to resolve the relationships among the Zygnematales, Coleochaetales, and Charales; however, they are consistent with previous phylogenomic studies in favoring that the morphologically complex Charales are not sister to land plants. [ABSTRACT FROM PUBLISHER]

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Charophytes (Streptophyta) represent a diverse assemblage of extant green algae that are the sister lineage to land plants. About 500-600+ million years ago, a charophyte progenitor successfully colonized land and subsequently gave rise to land plants. Charophytes have diverse but relatively simple body plans that make them highly attractive organisms for many areas of biological research. At the cellular level, many charophytes have been used for deciphering cytoskeletal networks and their dynamics, membrane trafficking, extracellular matrix secretion, and cell division mechanisms. Some charophytes live in challenging habitats and have become excellent models for elucidating the cellular and molecular effects of various abiotic stressors on plant cells. Recent sequencing of several charophyte genomes has also opened doors for the dissection of biosynthetic and signaling pathways. While we are only in an infancy stage of elucidating the cell biology of charophytes, the future application of novel analytical methodologies in charophyte studies that include a broader survey of inclusive taxa will enhance our understanding of plant evolution and cell dynamics., (© The Author(s) 2022. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

This paper examines the significance of the recent demonstration of polar auxin transport (PAT) in the green macroalga Chara (Charophyceae: Charales) and, especially, options for explaining some features of PAT in the Charales. The occurrence of PAT in the Charales shows that PAT originated in the algal ancestors of the embryophytes (liverworts, mosses, hornworts, and vascular plants), although it is not yet known if PAT occurs elsewhere in the Charophyceae or in other algae. While in the embryophytes PAT occurs in parenchymatously constructed structures which commonly also have xylem and phloem (or their bryophyte analogues) as long-distance transport processes in parallel to PAT, in Chara corallina PAT shares the pathway for long-distance transport of nutrients though the parenchymatously constructed nodal complexes and the single giant cells of the internode. The speed of auxin movement of PAT is much more rapid than that attributable to diffusion and of the same order as the rate of cytoplasmic streaming in the giant internodal cells, yet complete inhibition of streaming by the inhibitor cytochalasin H does not slow down auxin transport. Explanations for this phenomenon are sought in the operation of other mechanochemical motors, dynein–tubulin and kinesin–tubulin, as alternatives to the myosin–actin system which powers cytoplasmic streaming. Experiments in which microtubules are disrupted, for example by colchicine, could show if one of the tubulin-based motors is involved. If these motors are involved, some mechanism is needed to amplify the speeds known for the motors to explain the order of magnitude higher speeds seen for auxin transport. [ABSTRACT FROM AUTHOR]

The charophyte Lychnothamnus barbatus (Meyen) Leonh., in decline worldwide, is recorded in a new locality in Central Italy: the Lake of Martignano (Latium). It occurs with low coverage in a phytocoenose where Ceratophyllum demersum L. is dominant. [ABSTRACT FROM AUTHOR]

The development of DNA barcodes for green algae would aid in their accurate and rapid identification. This is particularly important for the green algae because in many species structural characters are few or difficult to observe. In this study we test the utility of several DNA barcode loci in seven distantly related species groups of freshwater charophytes and chlorophytes. The ITS rDNA and COI markers were the most variable, although COI was least applicable because it was successfully amplified and sequenced in only one test genus. The ITS1 and ITS2 rDNA regions each successfully amplified in only a subset of the charophytes. Both rbcL and tufA were moderately variable, although tufA may pose challenges in some lineages where the gene is encoded in the nucleus. The 18S rDNA and UPA were the least variable loci tested. Of the markers tested, rbcL, ITS2 and tufA (in chlorophytes) are the most promising for use as DNA barcodes. However, none of the loci tested were ideal for use across all tested lineages of green algae because of taxon-specific applicability, because none of the markers could distinguish closely related species in all groups tested, and because of overlap in the level of intraspecific and interspecific variation. [ABSTRACT FROM AUTHOR]

Charales populations from calcareous tropical streams in central Mexico were investigated through the sampling of six stream segments during the dry season, the most favourable growth period. Five taxa were found: Chara haitensis, C. vulgaris var. nitelloides, C. zeylanica var. diaphana, Nitella furcata var. sieberi and N. tenuissima var. tenuissima. Chara haitensis and N. tenuissima are reported for the second time in central streams and described in detail for the first time in the freshwater green algal flora from Mexico. Physical and chemical water quality data were also recorded in the investigated environments. All taxa were found at high temperatures (22-28 °C), neutral to moderately alkaline waters (pH 7-8) with high ionic content (total dissolved solids 593-1884 mg l-1, specific conductance 826-1952 μS cm-1), with sulfate-bicarbonate/calcium as dominant ions. The populations were associated with slow current velocity (≤ 30 cm s-1), shallow water depth (≤ 41 cm) and silt to sand substratum with high organic matter content. The taxa were found in a wide range of incident radiation (340-2234 μmol photons m-2 s-1), except for N. furcata var. sieberi which was found in shady sites (24 μmol photons m-2 s-1). All the populations investigated were found in mesotrophic to eutrophic conditions. [ABSTRACT FROM AUTHOR]

Chara globularis Thuillier (=f. globularis sensu R. D. Wood) is a widespread species of the genus and inhabits fresh- and brackish-water environments. In an attempt to reexamine the taxonomic status of C. globularis collected from Japan, we reassessed vegetative and oospore morphology of Japanese material and herbarium specimens originating from Europe (including the type specimen) and conducted molecular phylogenetic analyses based on rbcL gene sequences. Although the other vegetative morphologies were consistent with the description of C. globularis f. globularis sensu R. D. Wood, we identified two types of branchlets within the Japanese materials: one has elongate end segments (EL type), and the other has short end segments (SH type) corresponding to the type material. Moreover, the oospore wall of the EL type was different from that in the SH type. The oospores of the EL type were dark brown to reddish brown and had a spongy pattern with the pusticular elevations on the fossa wall, whereas the fossa wall of the SH type was black with a granulate to papillate or fine pusticular pattern. In addition, our sequence data demonstrated that these two types are separated phylogenetically from each other. Therefore, we describe the EL type as a new species, C. leptospora sp. nov. [ABSTRACT FROM AUTHOR]

Klebsormidium is a cosmopolitan genus of green algae, widespread in terrestrial and freshwater habitats. The classification of Klebsormidium is entirely based on morphological characters, and very little is understood about its phylogeny at the species level. We investigated the diversity and phylogenetic relationships of Klebsormidium in urban habitats in Europe by a combination of approaches including examination of field-collected material, culture experiments conducted in many different combinations of factors, and phylogenetic analyses of the rbcL gene. Klebsormidium in European cities mainly occurs at the base of old walls, where it may produce green belts up to several meters in extent. Specimens from different cities showed a great morphological uniformity, consisting of long filaments 6–9 μm in width, with thin-walled cylindrical cells and smooth wall, devoid of false branches, H-shaped pieces, and biseriate parts. Conversely, the rbcL phylogeny showed a higher genetic diversity than expected from morphology. The strains were separated in four different clades supported by high bootstrap values and posterior probabilities. In culture, these clades differed in several characters, such as production of a superficial hydro-repellent layer, tendency to break into short fragments, and inducibility of zoosporulation. On the basis of the taxonomic information available in the literature, most strains could not be identified unambiguously at the species level. The rbcL phylogeny showed no correspondence with classification based on morphology and suggested that the identity of many species, in particular the type species K. flaccidum (kütz.) P.C. Silva, Mattox et W. H. Blackw., needs critical reassessment. [ABSTRACT FROM AUTHOR]

The genus Nitella is the largest group in the Charales and has the highest diversity of vegetative and oospore morphologies. In his worldwide monograph on the Charales, R. D. Wood characterized the sections and species of Nitella mainly on the basis of vegetative morphology and treated oospore wall morphology as diagnostic at the infraspecific level. Therefore, many species of Nitella exhibiting distinct external morphology of the oospore wall (EMOW) were reduced to infraspecific rank and only 53 of 204 species previously described were recognized within Nitella. However, recent morphological and molecular phylogenetic studies have demonstrated the phylogenetic validity of using EMOW for diagnosing some species of Nitella. More recently, a scanning electron microscopy (SEM) study of internal morphology of the oospore wall (IMOW) and multiple DNA marker analyses using both nuclear and chloroplast gene sequences were conducted to improve our understanding of the taxonomy of Nitella at the species level, on the basis of cultured material of a large number of species. Multiple DNA marker analyses resolved detailed and robust phylogenetic relationships within the genus and demonstrated the taxonomic and phylogenetic significance of IMOW. In addition, they supported the taxonomic decisions based on differences in oospore morphology, suggesting that an integrated approach, involving both SEM studies of the EMOW and IMOW and multiple DNA marker analyses, is appropriate to address problems at lower taxonomic levels within the genus, as well as to construct a natural taxonomic system for the genus. In this paper, recent morphological and molecular phylogenetic studies are reviewed and recent improvements in taxonomy of Nitella are summarized. Moreover, the evolution of morphological features and phylogenetic relationships within Nitella are discussed, focusing especially on oospore morphology. [ABSTRACT FROM AUTHOR]

To elucidate the fundamental mechanisms and subsequent evolutionary aspects of plant cold acclimation, we examined the effect of cold acclimation on freezing tolerance in Klebsormidium flaccidum, a green alga belonging to Charophyceae, a sister group of land plants. Freezing tolerance of K. flaccidum was significantly enhanced by cold treatment: survival increased from 15% at −10 °C when grown at 18 °C to 55 and 85% after exposure at 2 °C for 2 and 7 d, respectively. Accompanying the development of freezing tolerance, soluble sugars (glucose and sucrose), a putative glycoside and amino acids, including γ-aminobutyric acid (GABA), accumulated to high levels in the alga, suggesting that these solutes play a crucial role in the cold acclimation of K. flaccidum. Interestingly, the application of abscisic acid (ABA) did not change the freezing tolerance of the alga. We also observed changes in cell structure, including increased numbers and sizes of starch grains in chloroplasts, chloroplast enlargement, vacuole size reduction and cytoplasmic volume increase. These results suggest that K. flaccidum responds well to cold treatment and develops freezing tolerance in a process comparable to that of land plants. [ABSTRACT FROM AUTHOR]

Chara braunii is a charalean species that grows in a range of aquatic habitats from shallow water in paddy fields to the bottom of deep lakes. More than 30 infraspecific taxa have been proposed within this species because of its morphological variability. In order to reexamine the infraspecific taxa and habitat preference of C. braunii, we carried out molecular phylogenetic analyses and quantitative measurements of morphological characters used for infraspecific taxa, based on samples collected from various habitats and localities in Japan. Sequence data from the gene encoding the large subunit of Rubisco (rbcL) and the intergenic spacer regions between the beta subunit of the ATP synthase and rbcL genes demonstrated two robust clades (groups A and B). Samples of group A were collected mainly from shallow aquatic environments (< 15 cm in depth) such as paddy fields, while those of group B were mainly composed of samples found in deep aquatic environments (> 1 m in depth) such as lakes or ponds. Groups A and B therefore seem to represent closely related entities that have recently differentiated and might adapt to two different aquatic environments. However, the morphological measurements suggested these groups can be delineated by neither of the traditional diagnoses that were different between infraspecific taxa of Japanese plants of C. braunii. [ABSTRACT FROM AUTHOR]

The taxonomic status of Nitella comptonii (Charales, Characeae) is not well understood because this species has not been recorded since the early 20th century, and detailed examinations of fully mature individuals have not been performed. Recently, we collected fully mature N. comptonii from the Okinawa Islands in Japan. These exhibited a distinctive fertile spherical head in the axils, and their vegetative and reproductive structures were consistent with those in the original description of the species. In 1965 in his ‘A revision of the Characeae’, R. D. Wood assigned N. comptonii as a subspecies of N. pseudoflabellata. In our study, scanning electron microscopic analysis of N. comptonii oospores revealed that external and internal oospore morphology of N. comptonii was clearly different from that of N. pseudoflabellata. In addition, multiple DNA phylogeny using the concatenated sequences of the chloroplast rbcL, atpB, and psaB genes, and nuclear 5.8S ribosomal RNA gene and internal transcribed spacer regions, clearly separated N. comptonii from N. pseudoflabellata. Therefore, N. comptonii should be classified as a separate species. [ABSTRACT FROM AUTHOR]

In an attempt to reconstruct the natural taxonomic system forNitella, 17 species ofNitellasubgenusTieffalleniawere reexamined using SEM observations of the internal morphology of the oospore wall (IMOW) and phylogenetic analyses of 4553 base pairs from multiple DNA markers (atpB,rbcL,psaB, and ITS-5.8S rRNA genes). Our SEM observations identified three types of IMOW: homogeneous (HG), weakly spongy (W-SG), and strongly spongy (S-SG) types. Based on differences in the IMOW, species with reticulate or tuberculate oospore wall ornamentation in the external morphology of the oospore wall (EMOW) were subdivided into two distinct groups (characterized by the HG or S-SG types of IMOW, respectively), which were robustly separated from each other in our molecular phylogenetic analyses. In our molecular phylogeny, the subgenusTieffalleniaconsisted of four robust monophyletic groups—three clades of the HG type and a spongy (S-SG and W-SG) type clade—that were characterized by differences in the IMOW and EMOW. In addition, our SEM observations and sequence data verified the distinct status of five species (N.japonicaAllen,N.oligospiraA. Braun,N.vieillardiistat. nov.,N.imperialisstat. nov., andN.morongiiAllen) that R. D. Wood had assigned as infraspecific taxa. Moreover, our SEM observations of the IMOW also suggested thatN.megaspora(J. Groves) Sakayama originally identified by LM includes at least two distinct species, characterized by W-SG and S-SG types of IMOW, respectively. [ABSTRACT FROM AUTHOR]

The main aim of this study was to investigate if the charophyte species Chara baltica, Chara canescens (two populations from the Baltic Sea (BS) and the Gulf of Korinth, Greece (GK)), and Lamprothamnium papulosum exhibit different acclimation capacities to irradiance. Growth, photosynthesis and pigment content were examined in the laboratory under six irradiance conditions (35–500 μmol photons m-2 s-1). Growth experiments showed increasing growth rates from 35 μmol photons m-2 s-1 (∼10 mg fresh weight (FW)) up to 70 μmol photons m-2 s-1 (∼20 mg FW) in C. baltica, from 35 μmol photons m-2 s-1 (∼15 mg FW) up to 380 μmol photons m-2 s-1 (∼145 mg FW) in C. canescens (BS), and up to the highest growth irradiance in algae of L. papulosum (35 μmol: ∼5 mg FW; 500 μmol: ∼20 mg FW). The species were tested for their ability to acclimate to different growth irradiances (Eg) by calculating Pmax (maximum photosynthesis rate at saturating irradiances), α (the efficiency of light utilization at limiting irradiance), and Ek (the light saturation point of photosynthesis, Pmax/α). All species exhibited increasing Pmax with increasing Eg. Whereas both populations of C. canescens increased α with increasing Eg, L. papulosum and C. baltica did not acclimate α at all. Ek, the irradiance at which photosynthesis ceased to be light-limited, was constant for all Chara species within the range of irradiances tested. Chl a/Chl b ratios of all species were constant over the whole range of Eg. Chl a/carotenoid ratios were constant in C. baltica, whereas Chl a/carotenoid ratios in L. papulosum and C. canescens (BS) decreased from 250 and 70 μmol photons m-2 s-1 upwards, respectively. Pigmentation analysis showed that Chl a/carotenoid acclimation was mainly caused by species-specific capacity to raise the content of lutein and carotene (C. canescens (BS), C. canescens (GK)) and xanthophyll cycle pigments (XCP; L. papulosum). The non-photochemical quenching (NPQ) capacities of L. papulosum, C. canescens (BS), and C. canescens (GK) were dependent from preacclimation status of algae, whereas NPQ of C. baltica was independent from growth irradiance.Our results indicate that C. baltica and C. canescens (BS) were light saturated within the chosen irradiances, whereas C. canescens (GK) and L. papulosum did not reach their limits of high-light acclimation. The photosynthetic pigments lutein, α- and β-carotene are suggested to act as photo-protective pigments in L. papulosum and C. canescens. [Copyright &y& Elsevier]

To gain insights into the phylogeny of charophytes and into their relationships with other green algae and bryophytes, we analyzed the chloroplast small and large subunit rRNA sequences of charophytes belonging to five orders (Charales, Coleochaetales, Desmidiales, Klebsormidiales, and Zygnematales), of chlorophytes from the four remaining classes of green algae, and of bryophytes representing the three classes reported in this group of land plants. We also probed the gene organization and intron content of the chloroplast rDNA operon in charophytes and bryophytes. The organization of this operon proved to be highly conserved, except in members of the Desmidiales and Zygnematales. Homologous group II introns were identified in the trnA (UGC) gene of all charophyte groups examined and in the trnI (GAU) gene of charophytes from all orders except the Desmidiales and Zygnematales. Phylogenetic analyses of concatenated rDNA sequences consistently placed the prasinophyte Mesostigma viride Lauterborn at the base of the Streptophyta and Chlorophyta, although alternative topologies positioning Mesostigma within the Streptophyta could not be rejected. A sister group relationship was unambiguously established between Chaetosphaeridium globosum (Nordstedt) Klebahn and members of the Coleochaetales. The Charales, Coleochaetales, Desmidiales, and Zygnematales were found to be monophyletic, and a sister group relationship was observed for the Desmidiales and Zygnematales. Although our analyses failed to resolve the branching order of the Coleochaetales, Charales, Desmidiales/Zygnematales, and bryophytes, they revealed that the problematic charophyte taxon Entransia fimbriata Hughes strongly clusters with Klebsormidium flaccidum (Kützing) Silva, Mattox et Blackwell to form a basal lineage relative to the other charophyte orders examined. [ABSTRACT FROM AUTHOR]