A CIRCADIAN RHYTHM IN THE LONG-DAY PHOTOPERIODIC INDUCTION OF ERECT AXIS DEVELOPMENT IN THE MARINE RED ALGA NEMALION HELMINTHOIDES1,2

Two isolates of Nemalion helminthoides from the west coast of Ireland showed a heteromorphic life history in which tetraspores formed under short-day conditions on uniaxial, prostrate tetrasporophytes gave rise to uniaxial, prostrate growths similar in morphology to the tetrasporophytes. The induction of multiaxial, erect axes on tetraspore-derived plants was a long-day photoperiodic response. At 11°C, 16:8 h LD, nitrate concentration in the enriched seawater medium had little effect on the numbers of erect exes formed. Induction of erect axes occurred only in daylengths ≥ 12 h, mainly between 7–13° C, and the critical daylength, which generally lies between 14 and 16 h, changed with temperature. Night-breaks (NB) of 1 h light in the middle of 16 h night were ineffective in the promotion of erect axis formation, and day-breaks (DB) of 1 h darkness in the middle of a 16 h day did not inhibit axis formation. Neither continuous light nor NB of 1–1.5 h given at various times during the dark period of an 8:16 h LD cycle promoted the formation of erect axes. At 9° C, equivalent photon exposures (0.69 and 0.34 mol·m^?2) at two different instantaneous photon flux densities resulted in erect axis formation only in the 14 h, 16 h and DB regimes. Photoregimes of 16 h light in combination with dark cycles of various lengths resulted in the maximal promotion of the formation of erect axes in diurnal (22–24 h) and bi-diurnal (44–48 h) cycles, a diminishing response in non-diurnal cycles greater than 24 and 48 h, and a minimal response at 32 h. These data show that the formation of erect axes is a long-day photoperiodic response and provide further evidence for a connection between endogenous circadian rhythms and long-day photoperiodic responses.     

PIT CONNECTION FORMATION IN THE RED ALGA PSEUDOGLOIOPHLOEA

Pit connection formation in the marine red alga Pseudogloiophloea confusa was studied with the electron microscope. The process of formation occurs in 2 stages. First, a septum forms as an annular ingrowth from the lateral walls. Lomasomes are associated with the centripetal accretion of wall material. The completed septum contains a large rimmed aperture, bounded by the continuous plasmalemma, and through which the cytoplasm is continuous from cell to cell. In the second stage, a highly structured plug is formed which completely blocks the aperture. The plug is condensed on flattened vesicles which lie parallel to one another and which traverse the aperture. The mature plug is composed of granules 50–100 A in diameter and surrounded by several dense layers which appear to enclose an 80 A limiting membrane. Once the pit connection is formed, no material is seen to traverse it.     

THE ROLE OF SECONDARY PIT CONNECTIONS IN RED ALGAL PARASITISM1

Secondary pit connections are common between cells of hosts and parasites in the widespread phenomenon of red algal parasitism. The DNA-specific fluorochrome 4′,-6-diamidino-2-phenylindole (DAPI) reveals that in host-parasite secondary pit connection (SPC) formation between the parasitic red alga Choreocolax polysiphoniae and its host Polysiphonia confusa, a nucleus and other cytoplasmic components of the parasite are delivered into the cytoplasm of a host cell. Host cells receive large numbers of parasite nuclei and these, apparently arrested in G¹, are maintained intact in host cells for periods of several weeks. Within these enlarged, differentiated cells, starch accumulates and cytoplasmic organelles proliferate as the central vacuole decreases in size. Host nuclear DNA synthesis is stimulated in the infected host cell, resulting in an increase in the number of host nuclei, or an increase in DNA in each of the existing host nuclei (i.e. somatic polyploidy). Occasionally, infected host cells will recommence division and engender a new host branch. Microspectrofluorometry of nuclear DNA quantitatively confirms not only the identity and transfer of parasite nuclei to host cells, but also the transfer of parasite nuclei to other parasite cells. Measurements also reveal that the single nucleus of Choreocolax becomes progressively more polyploid as cells become larger and more highly differentiated. Secondary pit connection formation between Choreocolax and Polysiphonia provides the mechanism for the transfer of parasite genetic information (via the parasite nucleus and cytoplasm) into the host. The parasite nuclei may thereby control and redirect the physiology of the host for the benefit of the parasite.     

STRUCTURE AND DEVELOPMENT OF THE CARPOSPOROPHYTE OF NEMALION HELMINTHOIDES (NEMALIONALES,RHODOPHYTA)1

Following fertilization, the carposporophyte of Nemalion helminthoides (Velley in With.) Batters differentiates into four distinct regions: the fusion cell, the sterile gonimoblast cells, the carposporangial mother cells and the carposporangia. The gonimoblast is formed by apically dividing, monopodial filaments of limited growth which may later become pseudodichotomous. Upon differentiation of a terminal carposporangium, a gonimoblast filament may continue to grow sympodially. A single carposporangial mother cell may produce carposporangia in several different directions as well as proliferate successive carposporangia within the sporangial walls that remain after carpospore liberation. As the carposporophyte matures, the gonimoblast initial, the stalk cell, the hypogynous and subhypogynous cells fuse. Except for the fusion cell, all cells of the carposporophyte show organelle polarity and contain a distally located, lobed chloroplast and proximal nucleus.     

A FREEZE-ETCHING STUDY OF THE RED ALGA PORPHYRIDIUM

Freeze-etched cells of Porphyridium cruentum and P. aerugineum closely resemble those fixed with glutaraldehyde and post-fixed with osmium tetroxide. Freeze-etching reveals diversity in the non-membranous and membranous parts of the cell. All the membranes are asymmetrical. The application of a double-replica technique illustrates how the two sides of several cell membranes fit together. Interpretation of fracture patterns through the thylakoids and stroma leads to the suggestion that the thylakoids are composed of repeating structural units. A model of the photosynthetic apparatus is proposed. It is suggested that the thylakoids of Porphyridium and other red algae are not always “free” but can be stacked much like those of other plants.     

AN ULTRASTRUCTURAL STUDY OF CELL DIVISION IN THE CAMBIUM

The fine structure of dividing cambial cells of Ulmus americana and Tilia americana has been studied in material fixed in glutaraldehyde followed by osmium tetroxide. The cambia examined consisted of 7–9 rows of unexpanded fusiform cells, all of which had similar ultrastructural components. The fine structure and sequence of events of mitosis and cytokinesis in the dividing cambial cells apparently are similar to those of dividing cells in root tips and leaves. Of special interest was the observation that during cytokinesis, a broad cytoplasmic plate or phragmosome precedes the developing phragmoplast and cell plate through the dividing cambial cell. Smooth and coated vesicles derived from dictyosomes are associated with cell plate formation in these cells, smooth vesicles primarily with earlier stages of plate formation, and coated vesicles in later stages.     

小麦珠心细胞的超微结构研究

本文报道衰退前的珠心细胞在发育过程中的超微结构变化。大多数珠心表皮细胞和离胚囊较远的珠心细胞有较大的核质比,细胞质中游离核糖蛋白体的密度较大;线粒体和质体数量较多,形态上也有较大变化;有具活跃分泌功能的高尔基体和少量或长或短的粗糙内质网槽库;细胞中有或多或少的小液泡,其中常常含有被消化的细胞质碎片;细胞壁上有很多纹孔和胞间联丝与邻近细胞相通。在离胚囊稍近的珠心细胞中,粗糙内质网迅速增生,出现平行内质网槽库和同心内质网环,后者在一定条件下有可能成为一种自噬结构。同心内质网环包围的细胞质被消化后往往形成小液泡。通过新液泡的形成,原有液泡的扩大和合并,珠心细胞形成大的中央液泡。这时,珠心细胞呈现薄壁组织细胞的典型特征。此后,胚囊进一步扩展??引起这些珠心细胞衰退和死亡。     

AN ULTRASTRUCTURAL STUDY OF THE RELATIONSHIP BETWEEN MICROTUBULES AND MICROFIBRILS IN COTTON (GOSSYPIUM HIRSUTUM L.) CELL WALL REVERSALS

The arrangement of cellulosic fibrils in the cell walls of cotton fibers is very unusual; rather than exhibiting a continuous spiraling in one direction, they intermittantly reverse their gyre. Microtubules that line the periphery of the protoplasm, subjacent to the plasmalemma, tend to parallel the deployment of the cell wall microfibrils. It was not known whether this parallelism persisted through the reversal. By studying tangential sections of the cell wall/protoplasmic interfaces at the reversals, we show that congruity continues even through the reversals. Colchicine treatment did not appear to inhibit cellulose synthesis but it did abolish microtubules in the cotton fiber cells and deranged normal cell wall microfibrillar orientation. Previously, cotton fibers have been shown to possess most of the familiar organelles, but we found two new features not reported heretofore. They are microfilaments and peculiar “polygonal structures” that appear to be associated with the plasma membrane.     

AN ULTRASTRUCTURAL STUDY OF GAMETES AND FERTILIZATION IN PATELLA VULGATA L.

Gametes of Patella vulgata L. have been studied using electronmicroscopy and their ultrastructure described. Changes in ultrastructureoccurring during and after fertilization have been characterized,especially those occurring in the cortical region. These changesinclude appearance of Golgi bodies, mitochondria and agglomerationsof microtubular material. Cortical granules disappear and glycogengranules begin to be degraded. (Received 13 February 1984;     

MORPHOLOGY AND REPRODUCTION OF THE RED ALGA ACROCHAETIUM PECTINATUM IN CULTURE12

The life history of the marine red alga Acrochaetium pectinatum (Kylin) Hamel was studied in unialgal culture using supplemented natural seawater media. The tetrasporophytes are larger than the gametophytes, have a compact filamentous basal system, and produce monosporangia and tetrasporangia. Mono-spores give rise to tetrasporophytes. Tetraspores develop into small gametophytes with unicellular bases. The gametophytes are heterothallic when small (usually less than 500 μ) but as some females become larger (2-3 mm) they produce spermatangia as well as carpogonia. Gametophytes may bear mono-sporangia in addition to carpogonia or spermatangia. These monospores give rise to gametophytes. Fertilization of the carpogonia has not been observed. The tetrasporophytes produce only monosporangia in day-lengths of 12-16 hr, but both tetrasporangia and monosporangia are formed in daylengths of 6–10 hr. Tetrasporangial production is reduced at 15 C compared with 10 C. Light intensity in the range of 5-200 ft-c (cool white fluorescent lighting) has no apparent influence on induction of tetrasporangia. Induction of tetrasporangia is not a photoperiodic response because their development is not inhibited by a brief light break in the middle of the dark period in short daylengths. Plastid morphology, origin, and frequency of sporangia and vegetative branching are variable during the ontogeny, and consequently are somewhat unreliable as taxonomic criteria. Differences in basal systems between gametophytes and tetrasporophytes also indicate that this feature, which is used to distinguish major subgeneric groupings in Acrochaetium, may not be as useful as previously thought.     

A COMPARATIVE STUDY OF THE RED ALGA GRATELOUPIA FILICINA (HALYMENIACEAE) FROM THE NORTHWESTERN PACIFIC AND MEDITERRANEAN WITH THE DESCRIPTION OF GRATELOUPIA ASIATICA, SP. NOV.

Morphological observations and molecular analyses of the red alga Grateloupia filicina (Halymeniaceae) from two geographically distant regions, eastern Asia (Japan and northern China) in the northwestern Pacific and Italy in the Mediterranean, reveal the presence of two distinct entities. Morphologically, the eastern Asian entity differs substantially from the Italian entity in the following ways: 1) thin and soft thalli with wider axes, 2) denser medullary filaments, 3) scattered reproductive structures over the entire thallus, and 4) a mature auxiliary cell that is oval and slightly larger than other ampullary cells. Phylogenetic analysis based on the ribulose-1,5-bisphosphate carboxylase/oxygenase gene ( rbc L) sequences revealed that the eastern Asian and Italian entities are phylogenetically far apart, strongly supporting the differentiation of these two entities at the species level. The eastern Asian entity is therefore described as a new species, Grateloupia asiatica. This species can be distinguished from most known species of Grateloupia that have widely flattened thalli by its compressed to narrowly flattened axes with numerous pinnate proliferations and from a few species with similar thalli by a particular combination of features, including a gelatinous texture, mostly simple and narrower axes, a thinner cortex, and the absence of catenate proliferations.     

拟南芥菜(Arabidopsis thaliana)子叶中蛋白体形成的超微结构和免疫电镜定位研究

本文对拟南芥菜(Arabidopsis thaliana)种子发育过程中贮藏蛋白的积累和蛋白体的形成进行了超微结构和免疫电镜定位的研究。常规超薄切片的电镜观察表明,在开花后第10天(10 DAF),高电子密度的蛋白质物质开始在子叶细胞的液泡中沉积。这一过程一直延续到种子接近成熟(14 DAF),这时液泡中充满了蛋白质物质,转变成为大的蛋白体。利用了该种植物主要种子贮藏蛋白之一的12 s球蛋白的单克隆抗体作为免疫探针,以蛋白质A-胶体金电镜技术对12 s种子蛋白进行了细胞内定位,证实了在液泡中积累的物质为种子贮藏蛋白。实验结果表明在拟南芥菜中,子叶细胞中的液泡是蛋白体的前体,肯定了蛋白体的发生起源于液泡的观点。本文还对应用胶体金电镜技术进行细胞内定位的某些问题作了初步探讨。     

IMMUNOLOCALIZATION OF AN α-1,4-GLUCAN LYASE IN YOUNG AND MATURE PARTS OF THE RED ALGA GRACILARIOPSIS SP. (RHODOPHYTA)

The enzyme α-1,4-glucan lyase (EC 4.2.2.13) was studied in cells of young and mature parts of the red alga Gracilariopsis sp. by using immunogold labeling in ultrastructural studies. In young tissues, the α-1,4-glucan lyase was observed at two different sites: around the starch granules in the cytosol and in the stroma of the chloroplast. In mature tissues, the α-1,4-glucan lyase was present only in the chloroplasts. The possible role of this starch-degrading enzyme in red algae is discussed.     

小煤炱科子囊壳超微结构研究

用扫描电镜对小煤炱科Meliolaceae的美座附丝壳Appendiculella calotroma(Desm.)Hoehnel和莫勒针壳炱Irenopsis molleriana(Wint.)Stev.的子囊壳进行观察的结果,发现它们的子囊壳都有一个小孔口,孔口周围有2～4层小圆柱形至椭圆形细胞;它们的子囊壳表面细胞呈疣状或乳突状,具纵向沟纹。其中美座附丝壳还有具横条纹的蠕虫状附属物,莫勒针壳炱有光滑的子囊壳刚毛。子囊壳表面孔口的发现为小煤炱目Meliolales的确立提供了直接的证据。     

AN EXPANDED SURVEY OF THE ULTRASTRUCTURE OF RED ALGAL PIT PLUGS1

The fine structure of pit plugs in 90 species of red algae was examined, bringing the total number of species in the continuing survey to 153. The organization of plug caps was confirmed to be a stable, predictable trait within thalli, between generations in heteromorphic life histories, and within the presently recognized orders, with one exception—the Acrochaetiales. Two forms of the outer cap were found in this group, a thin plate, as in the Nemaliales and Palmariales, and a dome, as in Batrachospermales and Corallinales. Variation of pit plug structure indicates that the Acrochaetiales are a heterogeneous assemblage and that pit plugs will be useful in reappraising their systematics. The systematic affinities of several species of uncertain affinities are clarified. Schmitziella endophloea Bornet et Batters is excluded from both orders, Corallinales and Acrochaetiales, with which it previously was allied. Although other ordinal attributions are not precluded by pit plug structure alone, pit plug structure is consistent with placement of Apophlaea sinclairii Harvey and Hildenbrandia rivularis (Liebman) J. Agardh in the Hildenbrandiales, Plagiospora gracilis Kuckuck, Schmitziella endophloea, and Wurdemannia miniata (Duby) J. Feldmann et Hamel in the Gigartinales, and Pseudorhododiscus nipponicus Masuda in the Palmariales.