Chitin-glucan complex in cell walls of the Peltigera aphthosa lichen

Cell walls and chitin-glucan complexes isolated from uneven-aged components of the thallus of the Peltigera aphthosa lichen were studied. The mass fraction of the cell wall and chitin-glucan complexes increased with age, but the content of nitrogen in these structures decreased with age. The basal area of the thallus was characterized by the largest mass fraction of the chitin-glucan complex from the dry mass of the thallus; the apical area, by the largest mass fraction of chitin in the complex. It was demonstrated that in P. aphthosa, the degree of deacetylation of chitin in the complex (depending on the age) was 33 and 54% in the apical and basal areas, respectively. The suggested method of functional analysis of chitin-glucan complexes for the presence of free amino groups in them can be used for studying other lichenified fungi.     

Chitin-glucan complex in cell walls of the Peltigera aphthosa lichen

Cell walls and chitin-glucan complexes isolated from uneven-aged components of the thallus of the Peltigera aphthosa lichen were studied. The mass fraction of the cell wall and chitin-glucan complexes increased with age, but the content of nitrogen in these structures decreased with age. The basal area of the thallus was characterized by the largest mass fraction of the chitin-glucan complex from the dry mass of the thallus; the apical area, by the largest mass fraction of chitin in the complex. It was demonstrated that in P. aphthosa, the degree of deacetylation of chitin in the complex (depending on the age) was 33 and 54% in the apical and basal areas, respectively. The suggested method of functional analysis of chitin-glucan complexes for the presence of free amino groups in them can be used for studying other lichenified fungi.     

纵胞藻切段再生的初步研究

作者将纵胞藻切成1.5—3mm长的切段,用PES培养液,室内漫射光进行培养,成功地得到大量纵胞藻再生植株。通过实验探讨,作者认为纵胞藻的切段再生现象可能是该种海藻营养繁殖的一种形式。     

Apical cells of brown algae with particular reference to Sphacelariales, Dictyotales and Fucales

Brown algae show a significant diversity in thallus forms, giving a great number of model systems for the study of many important morphogenetic mechanisms. Thallus growth in brown algae is diffuse, intercalary or apical. The latter takes place by means of one or more apical cells. Among the brown algal groups, Sphacelariales, Dictyotales and Fucales give the best examples of apical growth, and have been repeatedly used for the study of the morphogenetic role of apical cells. In Sphacelariales the apical cells appear strongly polarized, the polarity expressed also on the organization of the microtubule cytoskeleton. These cells show a type of growth that can be compared with tip growth of root hairs, moss protonemata, pollen tubes and fungal hyphae, and is called ‘tip-like growth’. The thallus of Dictyotales grows by the activity of one or more apical cells showing variable degree of polarity. These cells do not exhibit any type of apical growth. In Fucales the vegetative thallus develops by means of an active apical meristem, which includes a large apical cell. This cell does not show polar organization or apical growth. However, in germinating zygotes of Fucales a polar axis is established and during the first stages of development they show a typical tip growth. In the present paper, the available information on the structure and division pattern of apical cells is presented. Their morphogenetic role is discussed, in relation to polarity, cytoskeleton organization, and apical dominance.     

Meristoderm in Turbinaria conoides (Fucales,sargassaceae)

In Turbinaria conoides (J. Agardh) Kützing, the hapteron, thallus and receptacle meristoderm cells are columnar, polarized and have thick longitudinal walls. In the thallus apical cavity, however, these cells are elongate and possess cap-like structures and thin, longitudinal walls. The meristoderm cells, except for those present at the apical cavities and ostiole regions, are overarched by 1–5 extracellular layers that are deposited in an orderly manner.The histochemistry of the meristoderm suggests that its cell walls contain alginic acid, cellulose and sulphated polysaccharides. The extracellular layers and the materials in the cap-like structures contain a mixture of alginic acid and sulphated polysaccharides, and little cellulose. The possible role of meristoderm cells lining the apical cavity of the thallus and that of extracellular layers is discussed.     

THALLUS ORGANIZATION AND DEVELOPMENT IN THE FRUTICOSE LICHENASPICILIA CALIFORNICA,WITH COMPARISONS TO OTHER TAXA

Thallus organization is examined inAspicilia californicaRosentreter, a fruticose lichen known from several localities in central and southern California. The sprawling, terete thallus branches possess a dense central medulla of thick-walled, longitudinally oriented fungal cells. This central tissue emerges at branch apices to form a darkly pigmented fungal tip. Thallus development involves the apical extension of the tip to produce a fungal tissue over which a cylindrical algal layer and cortex will eventually be formed. Apical branches are initiated by furcation entirely within the fungal tip. Lateral branches, emerging from the lichenized thallus, arise as a divergent bundle of elongate fungal cells originating in the medulla. The photobiont appears to play no direct role in initiation of apical or lateral branches. It is concluded that thallus development inA. californicaoccurs with a relatively low degree of synchrony between mycobiont and photobiont growth, similar to the pattern observed in crustose lichens with prothallic growth. A rather similar type of thallus organization is observed inA. hispida, although in that species mycobiont growth and branch initiation appear to be somewhat more closely associated with algal cell proliferation. A squamuloseAspiciliafrom central Spain produces rhizomorphs that may sometimes become invested with an algal layer and cortex, resembling the thallus axes ofA. californica.     

纵胞藻切段再生的初步研究

作者将纵胞藻切成1.5—3mm长的切段,用PES培养液,室内漫射光进行培养,成功地得到大量纵胞藻再生植株。通过实验探讨,作者认为纵胞藻的切段再生现象可能是该种海藻营养繁殖的一种形式。     

Daylength and development in four species of Ceramiaceae (Rhodophyta)

Developmental patterns in four species of Ceramiaceae were determined using excised thallus apices grown under a range of light periods. Models of thallus development and organization based on these patterns are presented. Increased rates of apical cell division, greater growth of apical fragments and increased average cell size were found with increasing number of hours light per day between 8–16 and 16–8 h. No aspect of growth investigated was associated with photoperiodic phenomena, and growth occuring during the light break (8-7.5-1-7.5 h) was intermediate between that in 8–16 and 12–12 h. Three patterns of cell elongation were found in the four species in which (1) cell age, (2) cell age and position and (3) cell age, cell position and light period determined cell length at different axial cell positions. Elongation was followed within cells, along axes ofAntithamnion spirographidis for plants grown under different day lengths. Three regions of development were found along main axes: (1) an apical region in which basipetal expansion was greater than acropetal expansion. (2) a zone of stability with equal elongation in apical and basal growth region of cells, and (3) a basal region with greater acropetal expansion. With increasing daylength, the zone of stability was extended to greater ranges of cell length.     

Effect of gibberellin and kinetin on the regeneration ability ofFucus vesiculosus L.

The influence of gibberellic acid (GA³) and kinetin (6-furfurylaminopurine) on the regeneration ability of the basal and apical thallus fragments ofFucus vesiculosus L. was examined. The naturally occurring gibberellin and kinetin-like substances in these thallus fragments were also studied. It was found that exogenously applied GA³ markedly increased the number of adventitious branches formed on the cut surface of the thallus fragments taken from the apical parts of plants. The concentration of 0.001 mg GA³ I-1 proved to be the most effective. The growth promoting effect of GA³ was increased by simultaneous action with kinetin. In experiments in which the fragments of the basal parts of the thallus were treated with GA³, as a rule a slight growth inhibition was observed. The growth responses of the investigated plant tissues to gibberellin and kinetin varied according to season. Usually their susceptibility to the applied plant hormones was greater in spring than is summer. The shifts in growth reaction were related to the seasonal changes in the content of endogenous gibberellin and kinetin-like substances in the investigated parts of the thallus. It is suggested that growth regulators of the gibberellin and cytokinin type are involved in the regeneration processes inFucus.     

The Structure and Development of the Thallus in the British Species of Gelidium and Pterocladia

The apical structure and the development of the thalli of allthe British species of Gelidium and Pterocladia have been investigated;the development of G. pulchellum is described in detail. Eachaxis is terminated by one or more apical cells, which by theirsegmentation form the tissues of the thallus. An axial filamentis distinct for a short distance behind each apical cell, butsecondary pit-connexions develop rapidly so that in sectionthe mature axis has the appearance of a multi-axial structure. Lateral branches of the frond develop by the segmentation ofthe lateral branch apical cells, which are formed by the transformationof superficial cortical cells, either in the meristematic ormature parts of the axes. The extreme variability of externalappearance is due principally to the indeterminate origin ofall lateral branches. The thallus in the British species of Gelidium and Pterocladiaconsists of erect fronds borne on creeping axes. The relativeproportions of the frond and creeping axes in various speciesand their survival through adverse conditions are discussed.     

大型绿藻浒苔藻段及组织块的生长和发育特征

通过将浒苔叶状体分为基部、中部和顶端三部分分别进行切段和切碎处理,在实验室条件下,用液体浅层培养的方法,系统地研究了其组织和细胞的生长和发育特性。显微观察的结果显示：切段培养条件下,基部和中部的藻段均可在其形态学下端形成假根,在形态学上端产生类似叶状体的突起。藻段的发育具极性,但是其极性并不绝对的,在1.0 mm的基部藻段两端都观察到了假根的形成。虽然顶端的藻段和组织块全都形成和释放了孢子,未见明显的营养生长,但是在培养早期,其下端仍然具有形成假根的能力。浒苔各部位藻段和组织块释放的和滞留于孢子囊内的孢子都可以立即萌发成苗。快速生长的中基部藻段形成了气囊,致使其漂浮于培养基上。有很多藻段和组织块形成和释放了生殖细胞,释放到外界以及滞留于孢子囊内的孢子均可立即附着萌发。数据分析表明：藻段的生长具有极性,不同部位相同长度的藻段生长率差异明显,基部藻段的生长率高于中部藻段,顶部藻段无明显的营养生长。藻段的生长与其原始长度和在藻体中所处的位置有密切关系;藻段和组织块的再生与藻体的完整性及其在藻体中所处的位置有关。     

A Comparative Study of Free Amino Acids of the Brown Alga <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> Linnaeus, 1753 from the Intertidal Zone of the Murman Shore,Barents Sea

The free amino-acid contents of the apical and middle parts of the thallus, as well as the receptacles of fertile and juvenile specimens, of the brown alga Fucus vesiculosus collected from seven different biotopes of the Murman shore, Barents Sea have been studied for the first time. The free amino-acid composition of the studied algae specimens was dominated by alanine, along with aspartic and glutamic acid. The distribution of free amino acids in the thallus of Fucus is uneven and depends on the habitat. The free aminoacid contents in the spring vary considerably between different parts of the thallus; however, certain regular patterns of their distribution are observed. A correlation has been found between the level of some individual amino acids in different parts of the thallus of fertile and juvenile algae and the salinity of the seawater.     

Spatial organization of the three‐component lichen Peltigera aphthosa in functional terms

The cephalolichen Peltigera aphthosa (L.) Willd. is characterized by lateral heterogeneity, which manifests itself in the presence of three thallus zones, referred to as the apical, basal and medial zone. These zones differ in terms of interaction between lichen bionts and their physiological activity. The apical thallus zone is more efficient in establishing a contact with cyanobacteria, because of a higher lectin content and a larger overall thallus surface area due to the presence of numerous mycobiont hyphae. Cephalodia are formed in this zone. The interaction between the mycobiont and cyanobiont is more intense in the medial zone. However, the establishment of the contact with cyanobacteria in this zone less probable. The spatial distribution of lectins in the thallus was determined. To reveal the differences in photosynthetic activity in three thallus zones, transient analysis of chlorophyll a fluorescence and the assessment of non‐photochemical quenching of excited chlorophyll states were performed. Assimilation of absorbed light energy was more effective in the medial zone. The basal zone was characterized by decreased photosynthetic activity, lichen dissociation and thallus death.     

Cell wall physicochemical properties determine the thallus biomineralization pattern of Padina gymnospora (Phaeophyceae)

Approximately half of the Padina (Dictyotales, Phaeophyceae) species mineralize aragonite needles over the adaxial thallus surface, where mineral bands are interspersed with nonmineralized regions along the thallus from the apical to basal end. However, this calcification pattern and the related algal properties are not well understood. Therefore, this work was performed to elucidate a potential role of cell walls in the inhibition/induction of mineralization in the brown alga Padina gymnospora. In a comparison of specific thallus regions, differences were identified in the cellulose distribution, microfibrils arrangement and thickness, distribution and abundance of phenolic substances, and physical differences among the surfaces of the thallus (deformation, adhesion, topography, and nano‐rugosity). In vitro mineralization assays indicated that phenolic substances are strong modulators of calcium carbonate crystals growth. In addition, de novo mineralization assays over cell wall surfaces that were used as templates, even without cellular activity, indicated that the cell wall remains a key factor in the induction/inhibition of mineralization. Overall, the current findings indicate a strong correlation between the physico‐chemical and structural properties of the cell wall and the alternation pattern of the mineralization bands over the thallus of P. gymnospora.     

Structure and development of Nostoc strands in Leiosporoceros dussii (Anthocerotophyta): a novel symbiosis in land plants

The presence of Nostoc in longitudinally oriented schizogenous canals is a feature that separates Leiosporoceros from all other hornworts and represents a novel symbiotic arrangement in land plants. In surface view, Nostoc canals are visible as elongated, dichotomously branched blue-green strands. All other hornworts develop numerous discrete globose colonies through continuous production of mucilage clefts as avenues for multiple invasions within a single thallus. To elucidate the anatomy and development of the unusual Nostoc strands in Leiosporoceros, we examined sporeling development in culture and the structure of strands in field-collected plants using light and electron microscopy. Rosette-like sporelings have mucilage clefts scattered along swollen apices. All field specimens were strap-shaped, contained Nostoc, and lacked mucilage clefts. Nostoc strands are located in the center of the thallus and develop behind the apical cell by separation of the middle lamella between apical derivatives. Strands elongate and branch in synchrony with apical growth, and thus only a single invasion is required for strand production. Two distinct ultrastructural morphotypes in the collections suggest nonspecificity of Nostoc. We speculate that Nostoc enters the thallus in the sporeling stage through mucilage clefts, and once colonies are established, cleft production ceases.     

Content of Gibberellic Acid in Apical Parts of Male and Female Thalli of Chara Tomentosa in Relation to the Content of Sugars and Dry Mass

The contents of gibberellic acid (GA₃), glucose and starch, and dry mass in four nodes of apical parts of male and female thalli of Chara tomentosa were measured. The GA₃ concentration was about 4 times higher in male than in female thallus and about 10 times higher in the first node than in the next three nodes of both thalli. The apical part of male thallus contains 2.5 times less glucose and 1.7 times less starch than female one. The average amount of dry mass of male and female thallus was similar: 9.9 and 9.8 % of fresh mass. The findings of this investigation demonstrate the interdependence of gibberellic acid and sugars in development of male and female Chara tomentosa thalli.     

Reorganization of the actin and microtubule cytoskeleton throughout blue-light-induced differentiation of characean protonemata into multicellular thalli

Summary The reorganization of the actin and microtubule (MT) cytoskeleton was immunocytochemically visualized by confocal laser scanning microscopy throughout the photomorphogenetic differentiation of tip-growing characean protonemata into multicellular green thalli. After irradiating dark-grown protonemata with blue or white light, decreasing rates of gravitropic tip-growth were accompanied by a series of events leading to the first cell division: the nucleus migrated towards the tip; MTs and plastids invaded the apical cytoplasm; the polar zonation of cytoplasmic organelles and the prominent actin patch at the cell tip disappeared and the tip-focused actin microfilaments (MFs) were reorganized into a homogeneous network. During prometaphase and metaphase, extranuclear spindle microtubules formed between the two spindle poles. Cytoplasmic MTs associated with the apical spindle pole decreased in number but did not disappear completely during mitosis. The basal cortical MTs represent a discrete MT population that is independent from the basal spindle poles and did not redistribute during mitosis and cytokinesis. Preprophase MT bands were never detected but cytokinesis was characterized by higher-plant-like phragmoplast MT arrays. Cytoplasmic actin MFs persisted as a dense network in the apical cytoplasm throughout the first cell division. They were not found in close contact with spindle MTs, but actin MFs were clearly coaligned along the MTs of the early phragmoplast. The later belt-like phragmoplast was completely depleted of MFs close to the time of cell plate fusion except for a few actin MF bundles that extended to the margin of the growing cell plate. The cell plate itself and young anticlinal cell walls showed strong actin immunofluorescence. After several anticlinal cell divisions, basal cells of the multicellular protonema produced nodal cell complexes by multiple periclinal divisions. The apical-dome cell of the new shoot which originated from a nodal cell becomes the meristem initial that regularly divides to produce a segment cell. The segment cell subsequently divides to produce a single file of alternating internodal cells and multicellular nodes which together form the complexly organized characean thallus. The actin and MT distribution of nodal cells resembles that of higherplant meristem cells, whereas the internodal cells exhibit a highly specialized cortical system of MTs and streaming-generating actin bundles, typical of highly vacuolated plant cells. The transformation from the asymmetric mitotic spindle of the polarized tip-growing protonema cell to the symmetric, higher-plant-like spindle of nodal thallus cells recapitulates the evolutionary steps from the more primitive organisms to higher plants.Abbreviations FITC fluorescein isothiocyanate - MF microfilament - MT microtubule - MSB microtubule-stabilizing buffer - PBS phosphate-buffered saline     

Ultrastructural morphogenesis of dimorphic arcuate infection (gun) cells of Haptoglossa erumpens an obligate parasite of Bunonema nematodes

Haptoglossa is a genus of biflagellate organisms that has been placed in the oomycetes and is characterised by producing unique infective gun cells, which usually infect by physically rupturing the nematode cuticle. Haptoglossa erumpens is a parasite of Bunonema nematodes that produces arcuate infection cells and aplanospores that are discharged following the swelling and rupture of the thallus wall and distended host cuticle. Recent isolations of H. erumpens have revealed that the germinating aplanospores develop into two similar-sized but morphologically distinct infection cells. The uni-nucleate, convexly arcuate, gun cells were observed to fire in response to host nematodes, producing a cylindrical sporidium inside the host body. These gun cells had an apical missile chamber containing a needle with a unique arrangement of investing cones. Unlike previously described gun cells, the tube tail did not wind around the nucleus but continued into the basal vacuole where it terminated. The second type of infection cell was a concavely arcuate, bi-nucleate, cell that had an unusually large and elongate annulus component in the missile chamber. These modified bi-nucleate gun cells were never observed to fire in response to contact with Bunomena nematodes. The patterns of morphological and structural variations in these infection structures in this genus are reviewed in the light of these findings.     

Microscopic observations on tissue calcium distribution in the brown alga,Undaria pinnatifida (Harvey) Suringar

The distribution of Ca²⁺ in thallus tissues of the brown algaUndaria pinnatifida was investigated by microspectro-photometric analysis after fixation with Carnoy's reagent and staining with an alizarine sulfonate dye. Ca²⁺ accumulation in the young thallus was much higher in mucilage cells of the basal than the apical region; there was least in the pith of the basal region. A roughly uniform pattern was found in the stipe from the central part of the young thallus, while a highly irregular pattern occurred in both stipe and blade from the corresponding area of the mature thallus; the Ca²⁺ content was much lower than in the cortex, mucilage cells and vacuoles of the mature stipe than in the corresponding area of the young stipe. The contents of all regions of the mature blade were higher than those in the young blade; they were particularly high in mucilage cells.     

Phototropism of Thalli and Rhizoids Developed from the Thallus Segments of Bryopsis hypnoides Lamouroux

Newly regenerated thalli were used to study the phototropism of Bryopsis hypnoides Lamouroux under different qualities of light. Positive phototropism in the thalli and negative phototropiam In the rhizoida of B. hypnoides were investigated and analyzed in terms of bending. Both thaiii and rhlzoids developed from thallus segments exhibited typical tip growth, and their photoreceptive sites for phototroplam were also restricted to the apical hemisphere. The bending curvature of rhizoids and thalli were determined with unilateral lights at various wavelengths and different fluence rates after a fixed duration of Illumination. The trends of bending from the rhizoid and thallus were coincident, which showed that the action spectrum had a large range, from ultraviolet radiation （366.5 nm） to green light （524 nm）. Based on the bending curvatures, blue light had the highest efficiency, while the efficiency of longer wavelengths （〉500 nm） was significantly lower. External Ca^2＋ had no effect on the bending curvature of thalli and rhlzolda. Blue light （440 nm） induced thallus branching from rhizoids, while red light （650 nm） had no such effect. Fast-occurring chloroplast accumulation In the outermost cytoplasmic layer of the blue light （440 nm）-Irradiated region In the rhizoid was observed, from which protrusions （new thalli） arose after 4 h of the onset of illumination, and this action was thought to be driven by the dynamics of actin microfilamenta.