Phenylalanine ammonia-lyases and 4-coumaric acid coenzyme A ligases in Chara braunii, Marchantia polymorpha, and Physcomitrium patens as extant model organisms for plant terrestrialization.

The conquest of land posed severe problems to plants which they had to cope with by adapting biosynthetic capacities. Adaptations to respond to UV irradiation, water loss, pathogen and herbivore defense, and the earth's pull were essential. Chemical compounds alleviating these problems can be synthesized by the phenylpropanoid pathway, the core of which are three enzymes: phenylalanine ammonia-lyase (PAL), cinnamic acid 4-hydroxylase, and 4-coumaric acid coenzyme A-ligase (4CL). The genomes of model organisms, Chara braunii as aquatic alga and the two bryophytes Physcomitrium patens and Marchantia polymorpha, were searched for sequences encoding PAL and 4CL and selected sequences heterologously expressed in Escherichia coli for biochemical characterization. Several possible isoforms were identified for both enzymes in Marchantia polymorpha and Physcomitrium patens, while only one or two isoforms could be retrieved for Chara braunii. Active forms of both enzymes were found in all three organisms, although the catalytic efficiencies varied in a wide range. l-Phenylalanine was accepted as best substrate by all PAL-like enzymes, despite annotations in some cases suggesting different activities. The substrate spectrum of 4CLs was more diverse, but caffeic and/or 4-coumaric acids generally were the best-accepted substrates. Our investigations show that PAL and 4CL, important enzymes for the formation of phenolic compounds, are present and active in extant charophytes and bryophytes as model organisms for the conquest of land.

Mechanosensing and anesthesia of single internodal cells of Chara.

The giant (2-3 × 10-2 m long) internodal cells of the aquatic plant, Chara, exhibit a rapid (>100 × 10-6 m s-1) cyclic cytoplasmic streaming which stops in response to mechanical stimuli. Since the streaming - and the stopping of streaming upon stimulation - is easily visible with a stereomicroscope, these single cells are ideal tools to investigate mechanosensing in plant cells, as well as the potential for these cells to be anesthetized. We found that dropping a steel ball (0.88 × 10-3 kg, 6 × 10-3 m in diameter) through a 4.6 cm long tube (delivering ca. 4 × 10-4 J) reliably induced mechanically-stimulated cessation of cytoplasmic streaming. To determine whether mechanically-induced cessation of cytoplasmic streaming in Chara was sensitive to anesthesia, we treated Chara internodal cells to volatilized chloroform in a 9.8 × 10-3 m3 chamber for 2 minutes. We found that low doses (15,000-25,000 ppm) of chloroform did not always anesthetize cells, whereas large doses (46,000 and higher) proved lethal. However, 31,000 ppm chloroform completely, and reversibly, anesthetized these cells in that they did not stop cytoplasmic streaming upon mechanostimulation, but after 24 hours the cells recovered their sensitivity to mechanostimulation. We believe this single-cell model will prove useful for elucidating the still obscure mode of action of volatile anesthetics.

Dependence of cell's membrane potential on extracellular voltage observed in Chara globularis.

The membrane potential (Vm) of a cell results from the selective movement of ions across the cell membrane. Recent studies have revealed the presence of a gradient of voltage within a few nanometers adjacent to erythrocytes. Very notably this voltage is modified in response to changes in cell's membrane potential thus effectively extending the potential beyond the membrane and into the solution. In this study, using the microelectrode technique, we provide experimental evidence for the existence of a gradient of negative extracellular voltage (Vz) in a wide zone close to the cell wall of algal cells, extending over several micrometers. Modulating the ionic concentration of the extracellular solution with CO2 alters the extracellular voltage and causes an immediate change in Vm. Elevated extracellular CO2 levels depolarize the cell and hyperpolarize the zone of extracellular voltage (ZEV) by the same magnitude. This observation strongly suggests a coupling effect between Vz and Vm. An increase in the level of intracellular CO2 (dark respiration) leads to hyperpolarization of the cell without any immediate effect on the extracellular voltage. Therefore, the metabolic activity of a cell can proceed without inducing changes in Vz. Conversely, Vz can be modified by external stimulation without metabolic input from the cell. The evolution of the ZEV, particularly around spines and wounded cells, where ion exchange is enhanced, suggests that the formation of the ZEV may be attributed to the exchange of ions across the cell wall and cell membrane. By comparing the changes in Vm in response to external stimuli, as measured by electrodes and observed using a potential-sensitive dye, we provide experimental evidence demonstrating the significance of extracellular voltage in determining the cell's membrane potential. This may have implications for our understanding of cell membrane potential generation beyond the activities of ion channels.

Rediscovering Chara as a model organism for molecular and evo-devo studies.

Chara has been used as a model for decades in the field of plant physiology, enabling the investigation of fundamental physiological processes. In electrophysiological studies, Chara has been utilized thanks to its large internodal cells that can be easily manipulated. Additionally, Chara played a pioneering role in elucidating the presence and function of the cytoskeleton in cytoplasmic streaming, predating similar findings in terrestrial plants. Its representation considerably declined following the establishment and routine application of genetic transformation techniques in Arabidopsis. Nevertheless, the recent surge in evo-devo studies can be attributed to the whole genome sequencing of the Chara braunii, which has shed light on ancestral traits prevalent in land plants. Surprisingly, the Chara braunii genome encompasses numerous genes that were previously regarded as exclusive to land plants, suggesting their acquisition prior to the colonization of terrestrial habitats. This review summarizes the established methods used to study Chara, while incorporating recent molecular data, to showcase its renewed importance as a model organism in advancing plant evolutionary developmental biology.

Passive sampling of herbicides above sediments at sites with losses of submerged macrophytes in a mesotrophic lake.

Declines of submerged macrophytes (SUM) were monitored in littoral zones of the deep, mesotrophic lake Suhrer See (Northern Germany) since 2017. Drastic losses coincided with intense agriculture in sandy sub-catchments and precipitation. All lines of evidence pointed to a causal connection with subsurface discharge indicating that herbicide application might have caused the effects. Passive sampling was applied in 2022 to elucidate, whether herbicides were really present at sites of losses and if so, in ecotoxicological relevant concentrations. Samplers were exposed on top of lake sediments in 2 m depth and under worst case conditions, i.e., at sites, known for losses of the whole functional group of SUM and at the beginning of the vegetation period. At this time, SUM diaspores were most vulnerable to repression of development and the subsurface discharge was high in the same instance. The potential ecotoxicological relevance of detected herbicide concentrations was assessed with a toxic units (TU) approach, with reference to acute effect concentrations (EC50 of green algae, 72 h, growth). The TU ranged from 0.001 to 0.03. Most concentrations exceeded the threshold of relevance set by an assessment factor of 1000, i.e., TU > 0.001. Locally applied herbicides acted by suppressing developmental stages, and the sum of TU exceeded 0.02 at all sites, mainly due to diflufenican. Not applied locally, terbuthylazine and its relevant metabolites, including terbutryn, acted by inhibiting photosynthesis, and the sum of TU reached 0.005. On this base, diflufenican was assessed to be likely a main stressor, all other detected herbicides to be potentially relevant. Uncertainties and knowledge gaps were specified. The result of the chemical risk assessment was counterchecked for consistence with biological monitoring data within a whole lake perspective. Concepts of empirical and advanced causal attribution methodology were applied to get a grip to the ecological causal field and to protection.

Electrical Signals at the Plasma Membrane and Their Influence on Chlorophyll Fluorescence of Chara Chloroplasts in vivo.

Action potentials of plant cells are engaged in the regulation of many cell processes, including photosynthesis and cytoplasmic streaming. Excitable cells of characean algae submerged in a medium with an elevated K+ content are capable of generating hyperpolarizing electrical responses. These active responses of plasma membrane originate upon the passage of inward electric current comparable in strength to natural currents circulating in illuminated Chara internodes. So far, it remained unknown whether the hyperpolarizing electrical signals in Chara affect the photosynthetic activity. Here, we showed that the negative shift of cell membrane potential, which drives K+ influx into the cytoplasm, is accompanied by a delayed decrease in the actual yield of chlorophyll fluorescence F' and the maximal fluorescence yield Fm' under low background light (12.5 µmol m-2 s-1). The transient changes in F' and Fm' were evident only under illumination, which suggests their close relation to the photosynthetic energy conversion in chloroplasts. Passing the inward current caused an increase in pH at the cell surface (pHo), which reflected high H+/OH- conductance of the plasmalemma and indicated a decrease in cytoplasmic pH due to the H+ entry into the cell. The shifts in pHo arising in response to the first hyperpolarizing pulse disappeared upon repeated stimulation, thus indicating the long-term inactivation of plasmalemmal H+/OH- conductance. Suppression of plasmalemmal H+ fluxes did not abolish the hyperpolarizing responses and the analyzed changes in chlorophyll fluorescence. These results suggest that K+ fluxes between the extracellular medium, cytoplasm, and stroma are involved in the functional changes of chloroplasts reflected by transients of F' and Fm'.

Biodiversity, Ecology and Distribution of Mediterranean Charophytes in Southern Italy.

Charophytes are amongst the most endangered primary producers in freshwater and coastal ecosystems. In spite of the extensive research on the group and its ecological and conservational relevance, scarce information is available on Mediterranean environments, especially rivers and small water reservoirs, where charophytes face challenging summer droughts and changes in hydrological regimes, as well as pervasive anthropogenic pressures. This research aimed, through repeated field observations, detailed analyses of population traits, and extensive characterization of the colonized environments, to foster an understanding of the distribution, biodiversity, and ecology of charophytes in an area of exceptional environmental value and that is still uninvestigated in relation to its charophyte flora, the southern Campania region (Italy). Overall, 17 populations were discovered, belonging to 4 taxa of the Chara genus: C. globularis, C. gymnophylla, C. vulgaris, and C. vulgaris var. papillata, reduced to 12 populations and to the first 3 taxa by the end of the study. The species occupied different ecological niches and colonized environments such as rivers and small ponds, with environment-dependent morphotypes. The occurrence of few taxa with a wide distribution, often forming ephemeral populations, suggests ongoing constraints on charophyte biodiversity in the area, favoring opportunistic species that are able to benefit from temporary refugia.

Plasma membrane-chloroplast interactions activated by the hyperpolarizing response in characean cells.

Signaling pathways in plant cells often comprise electrical phenomena developing at the plasma membrane. The action potentials in excitable plants like characean algae have a marked influence on photosynthetic electron transport and CO2 assimilation. The internodal cells of Characeae can also generate active electrical signals of a different type. The so called hyperpolarizing response develops under the passage of electric current whose strength is comparable to physiological currents circulating between nonuniform cell regions. The plasma membrane hyperpolarization is involved in multiple physiological events in aquatic and terrestrial plants. The hyperpolarizing response may represent an unexplored tool for studying the plasma membrane-chloroplast interactions in vivo. This study shows that the hyperpolarizing response of Chara australis internodes whose plasmalemma was preliminary converted into the K+-conductive state induces transient changes in maximal (Fm') and actual (F') fluorescence yields of chloroplasts in vivo. These fluorescence transients were light dependent, suggesting their relation to photosynthetic electron and H+ transport. The cell hyperpolarization promoted H+ influx that was inactivated after a single electric stimulus. The results indicate that the plasma membrane hyperpolarization drives transmembrane ion fluxes and modifies the ionic composition of cytoplasm, which indirectly (via envelope transporters) affects the pH of chloroplast stroma and chlorophyll fluorescence. Remarkably, the functioning of envelope ion transporters can be revealed in short-term experiments in vivo, without growing plants on solutions with various mineral compositions.

Differentiation Disorders of Chara vulgaris Spermatids following Treatment with Propyzamide.

Microtubules are cytoskeletal cell elements that also build flagella and cilia. Moreover, these structures participate in spermatogenesis and form a microtubular manchette during spermiogenesis. The present study aims to assess the influence of propyzamide, a microtubule-disrupting agent, on alga Chara vulgaris spermatids during their differentiation by means of immunofluorescent and electron microscopy methods. Propyzamide blocks the functioning of the ß-tubulin microtubule subunit, which results in the creation of a distorted shape of a sperm nucleus at some stages. Present ultrastructural studies confirm these changes. In nuclei, an altered chromatin arrangement and nuclear envelope fragmentation were observed in the research as a result of incorrect nucleus-cytoplasm transport behavior that disturbed the action of proteolytic enzymes and the chromatin remodeling process. In the cytoplasm, large autolytic vacuoles and the dilated endoplasmic reticulum (ER) system, as well as mitochondria, were revealed in the studies. In some spermatids, the arrangement of microtubules present in the manchette was disturbed and the structure was also fragmented. The observations made in the research at present show that, despite some differences in the manchette between Chara and mammals, and probably also in the alga under study, microtubules participate in the intramanchette transport (IMT) process, which is essential during spermatid differentiation. In the present study, the effect of propyzamide on Chara spermiogenesis is also presented for the first time; however, the role of microtubule-associated proteins in this process still needs to be elucidated in the literature.

Calcium control of the hydraulic resistance in cells of Chara corallina.

The hydraulic resistance (the reciprocal of the hydraulic conductivity Lp) Lp-1 was measured in cells of Chara corallina by the method of transcellular osmosis. Treatment of cells with 100 mM KCl decreased Lp-1 significantly. Subsequent treatment of the cells with 70 mM CaCl2 recovered the decreased Lp-1 to the original value. To know whether K+ or Ca2+/Mg2+ acts on the cell wall and/or the membrane, the hydraulic resistances of the cell wall (Lpw-1) and that of the membrane (Lpm-1) were determined in one and the same cell. For this, a pair of cells (twin cells) were made from an internodal cell, one used for measurement of Lp-1 and the other used for the measurement of Lpw-1. From Lp-1 and Lpw-1, Lpm-1 was calculated. Both Lp-1 and Lpw-1 were decreased by K+, while Lpm-1 was not affected by K+. The same result was obtained with 5 mM EGTA. Lpw-1 was decreased more than it was by KCl but Lpm-1 remained constant after EGTA treatment. The recovery of the K+-decreased Lp-1 with Ca2+ can be explained exclusively by the recovery of Lpw-1 with Ca2+. The Ca2+ recovery of Lpw-1 was observed in the intact cell wall but not in the cell wall tube isolated from an internodal cell. The different response to Ca2+ between the intact cell wall and the isolated cell wall was discussed in relation to the tension in the cell wall which may be an important factor for the ionic regulation of hydraulic conductivity.

Evolution of long-distance signalling upon plant terrestrialization: comparison of action potentials in Characean algae and liverworts.

BACKGROUND: In this review, we summarize data concerning action potentials (APs) - long-distance electrical signals in Characean algae and liverworts. These lineages are key in understanding the mechanisms of plant terrestrialization. Liverworts are postulated to be pioneer land plants, whereas aquatic charophytes are considered the closest relatives to land plants. The drastic change of the habitat was coupled with the adaptation of signalling systems to the new environment. SCOPE: APs fulfil the 'all-or-nothing' law, exhibit refractory periods and propagate with a uniform velocity. Their ion mechanism in the algae and liverworts consists of a Ca2+ influx (from external and internal stores) followed by/coincident with a Cl- efflux, which both evoke the membrane potential depolarization, and a K+ efflux leading to repolarization. The molecular identity of ion channels responsible for these fluxes remains unknown. Publication of the Chara braunii and Marchantia polymorpha genomes opened up new possibilities for studying the molecular basis of APs. Here we present the list of genes which can participate in AP electrogenesis. We also point out the differences between these plant species, e.g. the absence of Ca2+-permeable glutamate receptors (GLRs) and Cl--permeable SLAC1 channel homologues in the Chara genome. Both these channels play a vital role in long-distance signalling in liverworts and vascular plants. Among the common properties of APs in liverworts and higher plants is their duration (dozens of seconds) and the speed of propagation (mm s-1), which are much slower than in the algae (seconds, and dozens of mm s-1, respectively). CONCLUSIONS: Future studies with combined application of electrophysiological and molecular techniques should unravel the ion channel proteins responsible for AP generation, their regulation and transduction of those signals to physiological responses. This should also help to understand the adaptation of the signalling systems to the land environment and further evolution of APs in vascular plants.

The molecular identity of the characean OH- transporter: a candidate related to the SLC4 family of animal pH regulators.

Characeae are closely related to the ancient algal ancestors of all land plants. The long characean cells display a pH banding pattern to facilitate inorganic carbon import in the acid zones for photosynthetic efficiency. The excess OH-, generated in the cytoplasm after CO2 is taken into the chloroplasts, is disposed of in the alkaline band. To identify the transporter responsible, we searched the Chara australis transcriptome for homologues of mouse Slc4a11, which functions as OH-/H+ transporter. We found a single Slc4-like sequence CL5060.2 (named CaSLOT). When CaSLOT was expressed in Xenopus oocytes, an increase in membrane conductance and hyperpolarization of resting potential difference (PD) was observed with external pH increase to 9.5. These features recall the behavior of Slc4a11 in oocytes and are consistent with the action of a pH-dependent OH-/H+ conductance. The large scatter in the data might reflect intrinsic variability of CaSLOT transporter activation, inefficient expression in the oocyte due to evolutionary distance between ancient algae and frogs, or absence of putative activating factor present in Chara cytoplasm. CaSLOT homologues were found in chlorophyte and charophyte algae, but surprisingly not in related charophytes Zygnematophyceae or Coleochaetophyceae.

Chara zeylanica J.G.Klein ex Willd. (Charophyceae, Charales, Characeae): First European Record from the Island of Sardinia, Italy.

The first record of a species belonging to the genus Chara L. subgenus Chara R.D.Wood section Grovesia R.D.Wood subsect. Willdenowia R.D.Wood from Europe is presented here, thus challenging the interpretation of its distribution pattern as an intertropical group of charophytes. The morphological characters of the specimens, as well as the results of a phylogenetic analysis, clearly identified them as Chara zeylanica J.G.Klein ex Willd. Although the subsection Willdenowia has yet to receive a thorough taxonomic treatment, a discussion of its relationship to other taxa of this subsection is provided despite the lack of a commonly agreed upon taxonomic concept. The ecological conditions of the Sardinian site of C. zeylanica are presented. Moreover, the status of and threats to this taxon, and hypotheses regarding potential pathways through which it reached Europe, are discussed.

Re-Establishment Techniques and Transplantations of Charophytes to Support Threatened Species.

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

Green Algal Models for Multicellularity.

The repeated evolution of multicellularity across the tree of life has profoundly affected the ecology and evolution of nearly all life on Earth. Many of these origins were in different groups of photosynthetic eukaryotes, or algae. Here, we review the evolution and genetics of multicellularity in several groups of green algae, which include the closest relatives of land plants. These include millimeter-scale, motile spheroids of up to 50,000 cells in the volvocine algae; decimeter-scale seaweeds in the genus Ulva (sea lettuce); and very plantlike, meter-scale freshwater algae in the genus Chara (stoneworts). We also describe algae in the genus Caulerpa, which are giant, multinucleate, morphologically complex single cells. In each case, we review the life cycle, phylogeny, and genetics of traits relevant to the evolution of multicellularity, and genetic and genomic resources available for the group in question. Finally, we suggest routes toward developing these groups as model organisms for the evolution of multicellularity.

Salinity-induced Changes in Gene Expression in the Streptophyte Alga Chara: The Critical Role of a Rare Na+ -ATPase.

The primarily freshwater genus Chara is comprised of many species that exhibit a wide range of salinity tolerance. The range of salt tolerance provides a good platform for investigating the role of transport mechanisms in response to salt stress, and the close evolutionary relationship between Charophytes and land plants can provide broader insights. We investigated the response to salt stress of previously identified transport mechanisms in two species of Chara, Chara longifolia (salt-tolerant), and Chara australis (salt-sensitive): a cation transporter (HKT), a Na+ /H+ antiport (NHX), H+ -ATPase (AHA), and a Na+ -ATPase (ENA). The presence of these candidate genes has been confirmed in both species of Chara, with the exception of the Na+ -ATPase, which is present only in salt-tolerant Chara longifolia. Time-course Illumina transcriptomes were created using RNA from multiple time points (0, 6, 12, 24 and 48 h) after freshwater cultures for each species were exposed to salt stress. These transcriptomes verified our hypotheses of these mechanisms conferring salt tolerance in the two species examined and also aided in identification of specific transcripts representing our genes of interest in both species. The expression of these transcripts was validated through use of qPCR, in a similar experimental set-up used for the RNAseq data described above. The RNAseq and qPCR data showed significant changes of expression mechanisms in C. longifolia (respectively), a down-regulation of HKT and a substantial up-regulation of ENA. Significant responses to salt stress in salt-sensitive C. australis show up-regulation of NHX and AHA.

Fluid-phase and membrane markers reveal spatio-temporal dynamics of membrane traffic and repair in the green alga Chara australis.

We investigated the mechanisms and the spatio-temporal dynamics of fluid-phase and membrane internalization in the green alga Chara australis using fluorescent hydrazides markers alone, or in conjunction with styryl dyes. Using live-cell imaging, immunofluorescence and inhibitor studies we revealed that both fluid-phase and membrane dyes were actively taken up into the cytoplasm by clathrin-mediated endocytosis and stained various classes of endosomes including brefeldin A- and wortmannin-sensitive organelles (trans-Golgi network and multivesicular bodies). Uptake of fluorescent hydrazides was poorly sensitive to cytochalasin D, suggesting that actin plays a minor role in constitutive endocytosis in Chara internodal cells. Sequential pulse-labelling experiments revealed novel aspects of the temporal progression of endosomes in Chara internodal cells. The internalized fluid-phase marker distributed to early compartments within 10 min from dye exposure and after about 30 min, it was found almost exclusively in late endocytic compartments. Notably, fluid cargo consecutively internalized at time intervals of more than 1h, was not targeted to the same vesicular structures, but was sorted into distinct late compartments. We further found that fluorescent hydrazide dyes distributed not only to rapidly recycling endosomes but also to long-lived compartments that participated in plasma membrane repair after local laser injury. Our approach highlights the benefits of combining different fluid-phase markers in conjunction with membrane dyes in simultaneous and sequential application modus for investigating vesicle traffic, especially in organisms, which are still refractory to genetic transformation like characean algae.

The role of ion-transporting proteins in the evolution of salt tolerance in charophyte algae.

Species within the genus Chara have variable salinity tolerance. Their close evolutionary relationship with embryophytes makes their study crucial to understanding the evolution of salt tolerance and key evolutionary processes shared among the phyla. We examined salt-tolerant Chara longifolia and salt-sensitive Chara australis for mechanisms of salt tolerance and their potential role in adaptation to salt. We hypothesize that there are shared mechanisms similar to those in embryophytes, which assist in conferring salt tolerance in Chara, including a cation transporter (HKT), a Na+ /H+ antiport (NHX), a H+ -ATPase (AHA), and a Na+ -ATPase (ENA). Illumina transcriptomes were created using cultures grown in freshwater and exposed to salt stress. The presence of these candidate genes, identified by comparing with genes known from embryophytes, has been confirmed in both species of Chara, with the exception of ENA, present only in salt-tolerant C. longifolia. These transcriptomes provide evidence for the contribution of these mechanisms to differences in salt tolerance in the two species and for the independent evolution of the Na+ -ATPase. We also examined genes that may have played a role in important evolutionary processes, suggested by previous work on the Chara braunii genome. Among the genes examined, cellulose synthase protein (GT43) and response regulator (RRB) were confirmed in both species. Genes absent from all three Chara species were members of the GRAS family, microtubule-binding protein (TANGLED1), and auxin synthesizers (YUCCA, TAA). Results from this study shed light on the evolutionary relationship between Chara and embryophytes through confirmation of shared salt tolerance mechanisms, as well as unique mechanisms that do not occur in angiosperms.

Age dependence of the hydraulic resistances of the plasma membrane and the tonoplast (vacuolar membrane) in cells of Chara corallina.

Hydraulic resistances (reciprocals of hydraulic conductivities) of the cell (Lp-1), the cell wall (Lpw-1), the membrane (Lpm-1), the plasma membrane (Lppm-1), and the tonoplast (Lptp-1) were determined in individual internodal cells of Chara corallina and their dependence on the cell age was studied. The thickness of the cell wall (d) was adopted as an index of the cell age, since the cell wall of spring-grown young cells (sg-cells) was found to be significantly thinner than that of winter-spent old cells (ws-cells). Both Lpw-1 and Lpm-1 were found to increase with cell age. Since Lpm-1 is the sum of Lppm-1 and Lptp-1, their dependence on the wall thickness was studied. It was found that both Lppm-1 and Lptp-1 increase with cell age using d as a proxy and that the former is distinctly higher than the latter. The ratio Lppm-1/Lptp-1 amounts to 30 for 5 µm of d, indicating that the tonoplast is a negligible barrier to osmotic water flow. The ratio decreases with the increase in d and amounts to 5.0 for 11 µm of d, showing that the tonoplast ages faster than the plasma membrane. The physiological meaning of the age dependence of hydraulic resistance of the tonoplast was discussed in terms of the role of the vacuole in the osmoregulation of the cytoplasm.

Surfactant and temperature as forcing functions on the growth of Egeria densa and Chara sp.: a modeling approach.

The wide use of detergents combined with rising water temperature is currently issuing of environmental concern. To evaluate the effect of sodium dodecyl sulfate (SDS) and temperature on macrophyte and talophyte growth, bioassays were conducted with distinct SDS concentrations (0.5 and 8.0 mg L-1) and temperatures (25 and 27 °C). The length of the Egeria densa and Chara sp. and the number and lengths of shoots were measured. Kinetic models were used to verify the temperature and SDS concentrations, as driving factors in the growth. The 2 °C increase in thermal condition interfered positively in both elongation and shoot development in the E. densa growth. For Chara sp., this tendency was not observed for the relative contribution of the shoots, but the number was higher at 25 °C. The higher concentrations of SDS (8.0 mg L-1) reduced the shoots' number and the relative contribution for Chara sp. and E. densa; meanwhile, the decrease in the growth coefficient was observed only for E. densa at 25 °C. In the Chara sp. development, the SDS addition interfered negatively in the growth coefficient. The predicted response of growth models will bring comprehensive knowledge of macrophytes and talophyte metabolism, and the interaction between plant species and forcing functions in modeling approaches will assist in finding the key processes driving plant growth under specific stressors.