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.     

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.     

巴尔干半岛现生轮藻植物综述

欧洲东南部巴尔干轮藻植物由于其产地生境的差异及以镶嵌状分布的模式,具有较高的生物分异度,计有44种,归属于现生属Nitella(10),Tolypella(4),Nitellopsis(1),Lychnothamnus(1),Lamprothamnium(1) and Chara(27).巴尔干半岛产有4种土著类型Chara rohlenae,Chara ohridana,Chara corfuensis and Chara visianii.建立1新种Chara hydropitys.该地区轮藻植物分布不均衡,部分类型例如Chara strigosa,Chara kokeilii,Chara muscosa,Chara fragifera,Chara imperfecta,Lychnothamnus barbatus为稀有品种,仅在少数地点发现.巴尔干地区轮藻植物之丰富多彩远远超过已知的程度,有待于深入研究.     

Some New Taxa and Records of Characeae in Hunan,China

In this paper, one new species, four new varieties and thirteen new records of Characeae from Hunan, China, are reported. They are Chara quadriscutulum, sp. nov., Nitella axilliformis var. biformis, var. nov., N. microcarpa var. unicarpa, var. nov., Chara braunii var. cylindrospora, var. nov., C. hydropitys var. hunanensis, var. nov., Nitella microcarpa Braun, N. leptoclada Braun, N. annandalei Pal, N. confervacea A. Braun, N. gracilliformis J. Groves, N. inversa Imahori, N. musashiensis Morioka, N. paucicostata T. F. Allen, N. acuminata var. gollmeriana (A. Br.) Zanev. et Wood, Tolypella boldii Sawa. Chara longifolia Robinson, C. pistianensis J. Vilhelm, C. grovesii Pal.     

Occurrence,composition, and structure of microbody crystalloids in charophycean gametangial sheath cells

Summary An ultrastructural study was made of the cellular sheaths surrounding the sexual organs of five species of algae in the three genera ofCharophyceae: Nitella flexilis, N. mirabilis, Chara brattnii, Tolypella boldii andT. intricata. Microbodies similar in appearance, with crystalline nucleoids, were present in the sheath cells of all five species. The microbodies resembled in size and topographical associations those of other green algae. The hexagonal-shaped crystalloids consisted of parallel arrays of fine tubules of about 15 nm in diameter arranged parallel to the long axis of the crystalloid. In cross sections of the crystalloid, the close packing of the tubules showed hexagonal arrays. The intertubular distance is about 7 nm. At higher magnification there is a suggestion that the walls of these tubules are themselves constructed of smaller tubules. Further electron microscopic observations of diaminobenzidine (DAB)-treated preparations revealed pronounced deposition of reaction product in the microbodies, particularly on the crystalloids. The reaction was completely blocked by the catalase inhibitor, aminotriazole. These results strongly suggest that catalase is involved in this reaction and that catalase is located in the crystalloids.     

湖北和江西省轮藻（Characeae）初报

最近五年(1980-1984)来。我们在湖北省西部和江西省南部的14个县、市,包括神农架林区,采集了若干轮藻标本。经过鉴定,得到此科植物二属、六种和二变种。这是此两个地区轮藻科植物的首次报告。     

Reconstruction of the former charophyte community out of the fructifications identified in Albufera de València lagoon sediments

Several decades ago, due to eutrophication, Albufera de València lagoon lost the charophyte meadows that covered the bottom in the past but had never been studied in detail. An area close to the lagoon will be restored now to improve water quality and to recover submerged vegetation. To have information on the background of the charophytes from this area, four 80-87 cm long sediment cores were extracted from the lagoon. The subfossil charophyte fructifications (oospores and gyrogonites) were isolated and identified in two of the four cores. Moreover, sediment core fractions from the third and fourth cores were allowed to germinate under several conditions. The study of the lagoon sediments has revealed that at least 11 morphologies of charophyte fructifications existed in the past. Ten of these were determined at species level: Chara vulgaris, Chara hispida, Chara aspera, Chara baltica, Chara tomentosa, Chara globularis, Lamprothamnium papulosum, Nitella hyalina, Tolypella glomerata and Tolypella hispanica. However, one form of Chara gyrogonite did not fit in any known species. L. papulosum oospores and gyrogonites were the most abundant and concentrated in the deepest sediment layers when the lagoon held brackish water. Large changes in salinity due to freshwater input drove charophyte species substitution (disappearance of L. papulosum). During the oligohaline period C. vulgaris sexual propagules were the most abundant. The last charophyte community before its disappearance due to eutrophication was composed mainly of C. hispida, C. tomentosa and N. hyalina (the two latter with small numbers of oospores in the sediment). To characterize the morphology of the unidentified gyrogonite species, 100 specimens were studied. This type could be a local variety of a more common species, probably C. vulgaris, grown under particular ecological conditions. Old collected oospores (more than 45 years old) germinated and could be identified as C. vulgaris and C. hispida.     

Raising the intracellular level of inositol 1,4,5-trisphosphate changes plasma membrane ion transport in characean algae.

Inositol 1,4,5-trisphosphate (InsP3) was introduced into the cytoplasm of characean algae in two different ways: (i) by iontophoretic injection into cytoplasm-enriched fragments from Chara and (ii) by adding InsP3 to the permeabilization medium of locally permeabilized cells of Nitella. In both systems this operation induced a depolarization of the membrane potential, ranging from a few mV to sequences of action potentials. The effect of InsP3 on locally permeabilized Nitella cells was abolished when InsP3 was added together with 30 mM EGTA. When inositol 1,4-bisphosphate or myo-inositol were substituted for InsP3 in this system, there was no change in the membrane potential. On the other hand, increasing the free Ca2+ concentration in the permeabilization medium induced, in a similar fashion to InsP3, action potentials. Similarities between InsP3 and Ca2+ action were also observed upon injection into Chara fragments. Both injections increased an inward current. In the first few seconds after injection the current/voltage characteristics of the InsP3-induced current resembled those of the Ca2(+)-sensitive current. Subsequently, differences between the InsP3- and Ca2(+)-induced phenomena became apparent in that the InsP3-induced current continued to increase while the Ca2(+)-induced current declined, returning to the resting level. Our results suggest that these plant cells contain an InsP3 sensitive system that, under experimental conditions, is able to affect membrane transport via an increase in cytoplasmic free Ca2+.     

A kinetic mechanism for the fast movement of Chara myosin

Endoplasmic streaming of characean cells of Nitella or Chara is known to be in the range 30-100 microm/second. The Chara myosin extracted from the cells and fixed onto a glass surface was found to move muscle actin filaments at a velocity of 60 microm/second. This is ten times faster than that of skeletal muscle myosin (myosin II). In this study, the displacement caused by single Chara myosin molecules was measured using optical trapping nanometry. The step size of Chara myosin was approximately 19nm. This step size is longer than that of skeletal muscle myosin but shorter than that of myosin V. The dwell time of the steps was relatively long, and this most likely resulted from two rate-limiting steps, the dissociation of ADP and the binding of ATP. The rate of ADP release from Chara myosin after the completion of the force-generation step was similar to that of myosin V, but was considerably slower than that of skeletal muscle myosin. The 19nm step size and the dwell time obtained could not explain the fast movement. The fast movement could be explained by the load-dependent release of ADP. As the load imposed on the myosin decreased, the rate of ADP release increased. We propose that the interaction of Chara myosin with an actin filament resulted in a negative load being imposed on other myosin molecules interacting with the same actin filament. This resulted in an accelerated release of ADP and the fast sliding movement.     

THE ASSOCIATION OF ROSETTE AND GLOBULE TERMINAL COMPLEXES WITH CELLULOSE MICROFIBRIL ASSEMBLY IN NITELLA TRANSLUCENS VAR. AXILLARIS (CHAROPHYCEAE)1,2

A freeze-fracture investigation of the putative cellulose synthesizing complex (terminal complex) morphology in Nitella translucens var. axillaris (A. Br.) R.D.W. internodal cells revealed single solitary EF globules and PF rosettes on the plasma membrane. The average density of rosettes in elongating internodal cells was 5.6 μm^?2 with slight spatial variation observed. In only three other algal genera (all zygnematalean) have rosette / globule terminal complexes been observed, while this characteristic is common to all vascular plants and one moss thus far investigated. This evidence strongly suggests that the rosette type of terminal complex morphology is an additional characteristic of charophycean algae and lends further support to the hypothesis that this group of algae represents the evolutionary line that gave rise to vascular plants. Observations were also made from the freeze-fracture of Nitella internodal cells concerning the orientation of cell wall microfibrils and cytoskeletal elements near the plasma membrane. The pattern of microfibril orientation in growing internodal cells is initially transverse to the cell long axis, becoming progressively axial presumably due to the strain of elongation. In mature internodal cells, the pattern of microfibril orientation is helicoidal. Microtubules appressed to the inner surface of the plasma membrane are oriented parallel to the most recently formed microfibrils in elongating and mature internodal cells.     

Some New Taxa of Charophyta in China

The authors examined specimens collected from Beijing, Hebei Province and North-east China. Two new species, one variety and five new records of the Characeae from China are reported in this paper. They are Nitella nenjiangensis sp. nov., Chara vertillibracteata sp. nov., C. globularis Thuiller var. beijingensis var. nov., Nitella axillaris Braun, N. crispa Imah., N. gracillima Allan, N. pseudoflabellata var. imperialis T. F. A., Chara arru-densis Mendes.     

Materials for the Charaphyta of China

Reported in this paper are two new species, one new variety, and three new records of the Characeae collected in China. They are Nitella anhuensis sp. nov., Chara paucicarpa sp. nov., Nitella alleninda var. tenuireticulata var. nov., N. gracilliformis J. Grove., N. formosa T. F. Allen and Chara tenuispina A. Br.     

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.     

Some new taxa of Nitelleae from Yunnan

Yunnan is extends across the subtropical and tropical zones, situated in the southern border area of southwestern China. This district is extremely rich in plants, and thus, it has been known as a “Kingdom of Plants”. However, up to the present our knowledge of the Charophyta in this region has been scanty. In order to get a thorough understanding of its Charophyta, we identified specimens collected from 13 countries or cities in this province. The result shows that is especially abundant in Charophyta. In this paper, however, only are reported new species, new varieties and new records of China on the Nitelleae. The former two are Nitella hokouensis, N. bicornuta, N. longicaudata, N. procera, N. brevidactyla, N. papillata, N. pseudohyalina, N. hyalina var. aberrans and Tolypella yunnanensis; while the third is Nitella globulifera Pal andN. japonica T. F. Alle     

Nuclear crystals, lampbrush-chromosome-like structures, and perinuclear cytoskeletal elements associated with nuclear fragmentation in characean internodal cells

Summary This article gives a survey of nucleus-associated structures and inclusions in a diverse range of characean algae includingChara braunii Gm.,Chara corallina Klein ex Willd., em. R.D.W.,Nitella cristata A.Br., em. R.D.W.,Nitella flexilis (L.) Ag.,Nitella furcata (Roxb. ex Bruz.) Ag. em. R.D.W.,Nitella hyalina (DC.) Ag.,Nitella pseudoflabellata A.Br., em. R.D.W.,Nitella pseudoflabellata var.imperialis T.F.A.,Nitella translucens var.axillaris (A.Br.) R.D.W. andNitellopsis obtusa (Desv. in Lois.) J.Gr. Lampbrushchromosome-like structures were found in nuclei ofNitella flexilis andNitellopsis obtusa and seem to be involved in the distribution of genetic material during nuclear fragmentation. Intranuclear tubular crystals of unknown protein composition were present in all species, especially in young, elongating cells, and could be important for establishing the main axis of the nuclei. Spindle-shaped protein crystals that originate in the nucleus and are released into the cytoplasm upon nuclear degeneration were observed in branchlet internodal cells of one population ofNitella flexilis. Perinuclear microtubules were present in all species, but perinuclear actin fibrils were hitherto only found in mostNitella species and inNitellopsis obtusa. None of these nucleus-associated structures seems to be responsible for the formation of constrictions leading to nuclear fragmentation. These constrictions were perpendicular to the main axis of the nucleus and symmetrical in theNitella species but asymmetric inC. braunii, C. corallina, and inNitellopsis obtusa. Statistical analysis of nuclear size, number and constriction sites indicate that fragmentation is a nonsynchronous process independent of the light-dark cycle.Abbreviations CLSM confocal laser scanning microscopy - DAPI 4,6-diamidino-2-phenylindole - DIC Nomarski differential interference contrast - LCLS lampbrush chromosome-like structure(s) Dedicated to Professor Walter Gustav Url on the occasion of his 70th birthday     

The effect of salinity on the reproduction of coastal submerged macrophytes in experimental communities

The effects of salinity on the reproduction of coastal submerged macrophyte species were studied on samples of communities from six seasonal marshes in two outdoor experiments performed in autumn and in spring. The submerged macrophyte communities were submitted to five different salinity levels (0, 1, 2, 4 and 6 g/1 Cl^?1). In a companion paper (Grillas, van Wijck & Bonis 1993) three groups of species were distinguished on the basis of their biomass production over the salinity range 0 to 6 g/1 Cl^?1: (1) glycophytes (non-salt-tolerant species), (2) salt-tolerant species and (3) halo-phytes. This part of the study describes the impact of salinity on the reproduction of the individual species during the two experiments. The species differ in their capacity to reproduce in the autumn; only Zannichelliapedunculata and Tolypella hispánica were able to produce fruits in that season. For all species reproduction was greater in spring and strongly correlated with biomass, except for Chara canescens. Differences in reproductive effort over the salinity range amplified the halophytic nature of Ruppia marítima and Chara canescens and the intolerance of Callitriche truncata and Chara contraria. For the other species, reproductive effort did not differ significantly over the salinity range. Regarding the effect of salinity on biomass and reproductive effort of individual species, there were large differences in the total weight of propagules produced at the community level and in the relative contribution of individual species. The resulting quantitative changes in the species composition of the seed bank could affect the structure of the communities by their effects on the establishment and survival of species populations.     

The Hydration-Induced Ca2+ Release Is a General Phenomenon in Characeae

When an internodal cell of Nitella axilliformis that had beentreated with 10 mM KCl and 1 mM EGTA was examined for transcellularosmosis, an increase in the cytosolic concentration of Ca²⁺on the endoosmotic side was observed, as was the case in Nitellaflexilis even though the increase was much smaller in Nitellaaxilliformis. The hydration-induced calcium release (HICR) wasalso observed in other species of Characeae, namely, Chara corallinaand Nitellopsis obtusa. HICR was also demonstrated in cytoplasmisolated from Nitella axilliformis and Chara corallina as fromNitella flexilis. Thus, it appears that HICR is not specificto Nitella flexilis but may be a general phenomenon in Characeae. ²Present adress: Department of Biology, Faculty of Science,Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263 Japan     

Offset of the vacuolar potential of Characean cells in response to electromagnetic radiation over the range 250 Hz-250 kHz

Measurements were made of the small, transient offsets of vacuolar potential produced in single cells of Nitella flexilis and Chara braunii by isolated bursts of audio frequency electromagnetic radiation. The offsets increased in magnitude with decreasing frequency of the electromagnetic radiation and, below about 6 kHz, seemed to approach a lowfrequency asymptote. This frequency dependence for the offset is shown to be in accordance with a previously developed model in which the incident radiation is weakly rectified by the cell's membrane system.     

The fine structure of mature spermatozoids of Chara corallina,with special reference to microtubules and scales

Summary New features recorded here for the first time include demonstration of the presence of a covering of tiny diamond shaped scales all over the body of the helical cell of the mature spermatozoids of Chara corallina Klein ex Willd. as well as a covering of slightly larger diamond shaped scales over the surfaces of the two flagella which has previously been seen by other authors in spermatozoids of both Chara and Nitella.The arrangement of microtubules in the anterior end of the spermatozoid, as a layer completely surrounding the anterior row of mitochondria resembles that of Chara fibrosa described by Pickett-Heaps 1968 and differs from that described for Nitella missouriensis by Turner 1968; these details are therefore perhaps phyletically significant.Other features such as the partial degeneration of the anteriorly placed flagellar bases are similar to those previously described for these two species although the distance between the bases and the point of emergence of the flagella from the body surface seems to differ somewhat from species to species.The investigation includes observations on the dehiscence of the antheridia and on the emergence of living cells from the spermatogenous filaments.The possible phyletic significance of some of these observations is discussed in a preliminary way.     

Radio-frequency bioeffects at the membrane level: Separation of thermal and athermal contributions in the characeae

Summary Single cells ofChara braunii andNitella flexilis were placed in a microstrip exposure apparatus and subjected to isolated bursts of radiofrequency irradiation. Their electrical responses were observed both extra- and intracellularly and found to be in accordance with theoretical predictions. In particular, the cell membrane displays rectifier-like behavior up to a cutoff near 10 MHz; this cutoff implies for the principal current carriers a transit time through the membrane of roughly 50 nsec and a mobility within the membrane approximately onefifth that of potassium in free solution. An electrical response of purely thermal origin was also detected; it was separated from the athermal rectifier response on the basis of rise time and frequency dependence. This is believed to be the first instance in which (i) a biological effect of radio-frequency radiation has had its thermal and athermal components clearly separated and (ii) a primary effect of ion transit time through the membrane has been directly detected.