Numerical taxonomy of some charophytes in Iran

Morphological characters of 10 species of Chara from different localities in northern, western and central Iran have been analyzed, with Nitella hyalina and Tolypella glomerata as outgroups. Phenetic and cladistics analyses of populations belonging to the 10 Chara species were undertaken to reveal their inter‐population morphological variation and inter‐specific relationships. Clustering was based on 54 characters (41 qualitative and 13 quantitative). This produced two major clusters, grouping Chara crassicauliss, C. vulgaris var. longibracteata, C. vulgaris var. vulgaris and C. contraria separate from C. grovesii, C. gymnophylla var. gymnophylla, C. gymnophylla var. rohlenae, C. kirghisorum and C. tomentosa. A smaller cluster of C. socotrensioides, C. fibrosa and Chara sp. was separate from these two clusters. A factor analysis identified the most variable morphological characters as type of cortification, prescence and length of the spine cells, stipulode length, type of branchlet cortication, bract cells length, placement of the gametangia, character of end segment, length of branchlet and internode, development of posterior bract cells, oogonia length and width, oospore length, width and length/width ratio, fossa breath, and number of striae.     

Photosynthetic characteristics of charophytes from tropical lotic ecosystems

Responses of photosynthetic rates, determined by oxygen evolution using the light and dark bottles technique, to different temperatures, irradiances, pH, and diurnal rhythm were analyzed under laboratory conditions in four charophyte species (Chara braunii Gmelin, C. guairensis R. Bicudo, Nitella subglomerata A. Braun and Nitella sp.) from lotic habitats in southeastern Brazil. Parameters derived from the photosynthesis versus irradiance curves indicated affinity to low irradiances for all algae tested. Some degree of photoinhibition, [β= ‐(0.30–0.13) mg O2 g^?1 dry weight Ir¹ (μmol photons m^?2 s^?1)^?1], low light compensation points (I_c= 4–20 μmol photons m^?2 s^?1) were found for all species analyzed, as well as low values of light saturation parameter (I_k) and saturation (I_s) 29–130 and 92–169 μmol photons m^?2 s^?1, respectively. Photoacclimation was observed in two populations of N. subglomerata collected from sites with different irradiances, consisting of variations in photosynthetic parameters (higher values of a, and lower of I_k and maximum photosynthetic rate, P_max, in the population under lower irradiance). The highest photosynthetic rates for Chara species were observed at 10–15°C, while for Nitella the highest photosynthetic rate was observed at 20–25°C, despite the lack of significant differences among most levels tested. Rates of dark respiration significantly increase with temperature, with the highest values at 25°C. The results from pH experiments showed highest photosynthetic rates under pH 4.0 for all algae, suggesting higher affinity for inorganic carbon in the form of carbon dioxide, except in one population of N. subglomerata, with similar rates under the three levels, suggesting indistinct use of bicarbonate and carbon dioxide. Diurnal changes in photosynthetic rates revealed a general pattern for most algae tested, which was characterized by two peaks: the first (higher) during the morning (07.00–11.00) and the second (lower) in the afternoon (14.00–17.00). This suggests an endogenous rhythm determining the daily variations in photosynthetic rates.     

Rare charophytes in Scotland's coastal saline lagoons

Summary

Recently collected data comparing the distribution and performance of the rare lagoonal charophyte Lamprothamnium papulosum across a number of UK coastal lagoon sites, including nine sites in the Western Isles, is presented. The surveys revealed that the species occurred over a wide range of salinities but was absent from sites with high phosphorus concentrations. The sites in the Western Isles held the most extensive populations and were least threatened by nutrient pollution. The discovery of two other endangered and vulnerable charophytes of brackish water, Tolypella nidifica and Chara baltica, at two of the Western Isles sites further highlights the importance of Scotland's saline lagoon resource. The use of the autoecological data on salinity and nutrient conditions for supporting Biodiversity Action Plan implementation for Lamprothamnium papulosum and for saline lagoon conservation in general is considered. Status summaries for all the charophyte species of brackish water recorded in Scotland are also provided.     

Seventy years of changes in the abundance of Danish charophytes

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Primary cell wall composition of bryophytes and charophytes

Major differences in primary cell wall (PCW) components between non-vascular plant taxa are reported. (1) Xyloglucan: driselase digestion yielded isoprimeverose (the diagnostic repeat unit of xyloglucan) from PCW-rich material of Anthoceros (a hornwort), mosses and both leafy and thalloid liverworts, as well as numerous vascular plants, showing xyloglucan to be a PCW component in all land plants tested. In contrast, charophycean green algae (Klebsormidium flaccidium, Coleochaete scutata and Chara corallina), thought to be closely related to land plants, did not contain xyloglucan. They did not yield isoprimeverose; additionally, charophyte material was not digestible with xyloglucan-specific endoglucanase or cellulase to give xyloglucan-derived oligosaccharides. (2) Uronic acids: acid hydrolysis of PCW-rich material from the charophytes, the hornwort, thalloid and leafy liverworts and a basal moss yielded higher concentrations of glucuronic acid than that from the remaining land plants including the less basal mosses and all vascular plants tested. Polysaccharides of the hornwort Anthoceros contained an unusual repeat-unit, glucuronic acid-alpha(1-->3)-galactose, not found in appreciable amounts in any other plants tested. Galacturonic acid was consistently the most abundant PCW uronic acid, but was present in higher concentrations in acid hydrolysates of bryophytes and charophytes than in those of any of the vascular plants. Mannuronic acid was not detected in any of the species surveyed. (3) Mannose: acid hydrolysis of charophyte and bryophyte PCW-rich material also yielded appreciably higher concentrations of mannose than are found in vascular plant PCWs. (4) Mixed-linkage glucan (MLG) was absent from all algae and bryophytes tested; however, upon digestion with licheninase, PCW-rich material from the alga Ulva lactuca and the leafy liverwort Lophocolea bidentata yielded penta- to decasaccharides, indicating the presence of MLG-related polysaccharides. Our results show that major evolutionary events are often associated with changes in PCW composition. In particular, the acquisition of xyloglucan may have been a pre-adaptive advantage that allowed colonization of land.     

Decline of charophytes during eutrophication: comparison with angiosperms

1. Charophytes have disappeared from several enriched lakes in Scania (southern Sweden) since the 1940s. Poor light conditions, rather than a toxic effect of phosphorus or negative impact of fish, are the most probable reason for this decline. 2. Small species of charophytes (shoot diameter 0.5–1.0 mm), which are able to form dense, low mats, still occur in eutrophic lakes with high phosphorus concentrations, but are restricted to areas of shallow water. In contrast, large species (shoot diameter 1–4 mm) have totally disappeared from the most turbid lakes. I suggest that these species are unable to grow in very shallow water because of damage by ice and wave action. 3. Maximum depth distribution (z_e) and Secchi depth (D) were measured in Scanian lakes for both charophytes and angiosperms and combined with data obtained from Chambers & Kalff (1985). According to the combined data, z_c and D are closely correlated with each other for both angiosperms and charophytes. 4. The z_c of charophytes is higher than z_c of angiosperms in clear lakes but lower in turbid lakes. Higher z_c of angiosperms in the most turbid lakes is explained by special adaptations of these species to poor light availability (shoot elongation, canopy formation, rapid growth during spring).     

Interaction of the Bacillus sphaericus mosquito larvicidal proteins

Genes for 51.4- and 41.9-kDa insecticidal proteins of Bacillus sphaericus were separately cloned and expressed in Escherichia coli. Both proteins were required for toxicity. Approximately equal numbers of cells containing the 51.4- and 41.9-kDa proteins produced the greatest toxicity; excess 41.9-kDa protein did not affect toxicity, whereas excess 51.4-kDa protein reduced activity. Larvae were killed when 41.9-kDa protein was fed up to 24 h after the 51.4-kDa protein, but not when the order of feeding was reversed. Radiolabelled toxins bound in approximately equal amounts to the gastric caecum and posterior midgut of Culex quinquefasciatus larvae. Radiolabelled 51.4-kDa protein was rapidly degraded by ca. 12-13 kDa in the larval gut, while 41.9-kDa protein was degraded by 1-2 kDa. Nonreduced toxin extracted from B. sphaericus produced a band on SDS-PAGE of ca. 68-74 kDa that contained both 51.4- and 41.9-kDa proteins based on sequence analysis, and a band of ca. 51 kDa that contained primarily 41.9-kDa protein. Escherichia coli containing 51.4-kDa protein enhanced toxicity of the latter eluted SDS-PAGE band. These proteins may associate very strongly, and trace amounts of 51.4-kDa protein in preparations of 41.9-kDa protein from B. sphaericus may be responsible for the previously reported toxicity of the latter.     

The cell biology of charophytes: Exploring the past and models for the future

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.

Charophytes constitute a diverse array of green algal taxa that provide critical insight into plant evolution and offer exciting opportunities for multiple levels of study in plant cell biology.     

Repellent, larvicidal and pupicidal properties of essential oils and their formulations against the housefly, Musca domestica

The essential oils of six plant species [peppermint, Mentha piperita, and bergamot mint, Mentha citrata (both, Lamiales: Lamiaceae); blue gum, Eucalyptus globulus (Myrtales: Myrtaceae); lemongrass, Cymbopogon citratus, and khus grass, Vetiver zizanoides (both, Poales: Poaceae), and turmeric, Curcuma longa (Ziniberales: Zingiberaceae)] were screened for repellent, larvicidal and pupicidal activities against the housefly, Musca domestica L. (Diptera: Muscidae). Subsequently, emulsifiable concentrate (EC) formulations of the two most effective oils were prepared and tested in the laboratory as well as in the field. In repellency bioassays, M. piperita (RC(84) , 61.0 μg/cm(2) ) was found to be most effective, followed by E. globulus (RC(84) , 214.5 μg/cm(2) ) and C. citratus (RC(84) , 289.2 μg/cm(2) ). Formulated M. piperita and E. globulus showed RC(84) values of 1.6 μg/cm(2) and 4.1 μg/cm(2) , respectively. Formulated M. piperita and E. globulus achieved larval mortality (LC(50) ) in 72 h at 5.12 μg/cm(2) and 6.09 μg/cm(2) , respectively. In pupicidal bioassays, crude oils of M. piperita and E. globulus suppressed the emergence of adult flies by 100%. Field experiments with the M. piperita formulation showed reductions in fly density (number of flies/h) of 96% on treated cattle and 98% on treated plots. This study demonstrates the effectiveness of EC formulations of selected essential oils in reducing housefly populations in field conditions.     

Oospore dimensions and wall ornamentation patterns in Swedish charophytes

The ultrastructural features of oospore wall ornamentation patterns revealed by scanning electron microscopy are important taxonomic characters of the Charales. The present study shows inter-and intrapecific variations in 19 species of the genera Chara, Lamprohamnium, Nitella and Tolypella. This is the first time that the oospore wall ornamentation of Swedish Charales has been documented in detail. In the studied Chara species the ornamentation within species was variable, and partly overlapping between species, but only between closely related species. In contrast, the Nitella species showed distinct differences in ornamentation patterns between species, although the same patterns can be found in different species. This study presents for the first time SEM images of the species Chara rudis (pustular ornamentation), Nitella opaca (pitted ornamentation) and Nitella wahlbergiana (anastomosing network ornamentation). The ornamentation pattern in the Nordic species TV. wahlbergiana , supports its separation from Nitella mucronata which has a reticulate ornamentation. The relationship between length and width of the oospores is also of taxonomic significance. Nitella and Tolypella oospores are roundish, whereas those of Chara and Lamprothamnium are elongate. The extent to which environmental and genetic factors can affect oospore size and shape within a species are still unknown, but in the present study both ornamentation pattern and size provided evidence for the distinction between Chara globularis and Chara aspera. Some further taxonomic problems in the Charales are discussed in the light of the results of this study.     

Study of some environmental factors affecting the occurrence of charophytes in Western India

Summary The occurence of charophytes in different regions of Western India is correlated with pH, hardness of water, calcium, magnesium, sulphates and phosphates concentrations in waters. Combined effect of some of these factors on the occurrence of charophytes was ascertained with the help of Cop-Chet punched card method. C. zeylanica and C. corallina have large ecological amplitudes. Sulphate has been the limiting factor for some of the species of charophytes.     

Mosquito larvicidal activity of polyacetylenes from species in the Asteraceae

Twenty-four polyacetylenes isolated from species in the Asteraceae were screened for their near-UV-mediated larvicidal properties to the mosquito, Aedes aegypti. Dosage resonse lines for three of the most active compounds were prepared. One of these, σ-terthienyl from Tagetes was more toxic than DDT when near-UV radiation was provided. A scaled up trial with this compound in a simulated field situation demonstrated its potential as a larvicide. The effects of the radiation dose on larval survival were studied and the action spectra for the phototoxic effects of three compounds on larvae were obtained with narrowband interference filters. Because of the close agreement between the action and absorption spectra, it appears most probable that the polyacetylene is the primary absorbing compound. The potential of polyacetylenes as larvicides and their role in plant herbivore relations are discussed.     

New finds of charophytes in Iceland with an update on the distribution of the charophyte flora

Charophyte species new to the flora of Iceland are reported and an update on the distribution of the previously known species is given. Four species are new to Iceland; Chara aspera Willdenow, Chara contraria Braun ex Kützing, Tolypella canadensis Sawa and Tolypella glomerata (Desvaux) Leonhardi, while four species were previously known: Chara globularis Thuiller, Chara virgata Kützing, Nitella flexilis (L.) Agardh and Nitella opaca (Agardh ex Bruzelius) Agardh. The finding of the species new to Iceland add to the hitherto known worldwide distribution of those species, including a significant extension to the north.     

The seasonal effects on the encrustation of charophytes in two hard‐water lakes

Encrustation and element content of six charophyte species from two hard‐water lakes were investigated monthly for a period of 1 year. Seasonal patterns were analyzed for the interaction of water chemistry. Encrustation followed a seasonal pattern for Chara contraria, Chara subspinosa, and Nitellopsis obtusa in Lake Krüselin and for Chara globularis and Chara tomentosa in Lake Lützlow. However, no seasonality in the precipitated CaCO₃ was observed for C. subspinosa in Lake Lützlow and for C. tomentosa in Lake Krüselin, indicating a lake‐specific dependency. Species‐specific encrustation was found. Chara contraria and N. obtusa encrusted the most in June and August, whereas C. subspinosa and Nitella flexilis/opaca exhibited lowest encrustation in March and April. The precipitated CaCO₃ of charophytes correlated negatively to the concentration of total inorganic carbon in both lakes. Element content of plant dry weight was species‐specific for Ca and K, and lake‐specific for Mg. No specific pattern was found for the TP and Fe contents. The results showed seasonal, species, and lake‐specific influences on the encrustation of charophytes.     

Acetylcholinesterase inhibitory activity of stigmasterol & hexacosanol is responsible for larvicidal and repellent properties of Chromolaena odorata

BackgroundChromolaena odorata, has been traditionally known for its insect repellent property. Aim of this study was to determine larvicidal tendency of C. odorata on Culex quinquefasciatus and isolate compounds responsible for this activity and to determine the mechanism of action of these compounds.MethodsC. odorata plant extract was screened for mosquito larvicidal activity. The extract was fractionated using chromatography and the bioactive fraction showing larvicidal activity was identified. The chemical nature of the compounds in the bioactive fraction was determined using NMR and Mass spectrometry.ResultsWe identified phytosterols and alkanols to be the compounds regulating larvicidal activity in the bioactive fraction of the plant extract. Stigmasterol and 1-hexacosanol were identified to be the chief orchestrators of larvicidal activity and their mode of action has been observed to be neurotoxicity. At a molecular level both stigmasterol and 1-hexacosanol were found to be inhibiting acetylcholinesterase activity in C. quinquefasciatus & A. aegypti. The acetylcholinesterase inhibitory effect was validated in vitro using recombinant acetylcholinesterase and ex vivo in larval homogenates of Culex and Aedes. Electrophysiological studies using electroantennography have shown enhanced neural response to these compounds.ConclusionsNeurotoxic effect of C. odorata derived stigmasterol and 1-hexacosanol, exerted through acetylcholinesterase inhibition was responsible for the mortality of C. quinquefasciatus, A. aegypti & Chironomus riparius. EAG studies pointed out hyper-excitability of the olfactory system by these compounds.General significanceThese compounds are natural agents for mosquito control that can be used in vector control as larvicidal compounds, pending further investigations.     

Ribosomal RNA sequence comparisons demonstrate an evolutionary relationship betweenZygnematales and charophytes

The nuclear-encoded small subunit ribosomal RNA (rRNA) sequences were determined forGenicularia spirotaenia, Mesotaenium caldariorum, andStaurastrum spec. (Zygnematales) to elucidate the evolutionary position of these green algae. Results of neighbour-joining and maximum parsimony phylogenetic analyses support a monophyletic origin of theZygnematales within the evolutionary assemblage defined by theCharophyceae (sensuMattox & Stewart) and land plants. TheZygnematales/Charophyceae/land plants are evolutionarily distinct from the monophyletic lineage defined by theChlorodendrales, Pseudoscourfieldiales, and theMicrothamniales/Chlorophyceae. In memoriamRobert W. Hoshaw.