A mechanism of propagule release from unilocular reproductive structures in brown algae

Summary The structure of unilocular sporangia inP. littoralis was investigated along with several other species of brown algae in order to study the mechanism by which propagules are released from unilocular reproductive structures. Unilocular sporangia inP. littoralis are composed of a spherical cell wall of two distinct layers and contain a number of zoospores. The mass of spores is surrounded and permeated by mucilaginous carbohydrates. It is suggested that the production of these carbohydrates generates the necessary pressure to weaken the sporangial wall. In addition, ultrastructural observations indicate that further weakening seems to occur due to digestion of the inner wall layer. Walls of sporangia were mechanically broken just prior to normal spore release in order to investigate whether internal pressure exists, and if it can effect spore discharge. Results show that an internal pressure does exist prior to normal spore discharge and that this pressure is not generated by turgor pressure of the spores themselves or by a semi-permeable wall osmoticum system. The discharge of spores seems to occur when the carbohydrate around the spores swells. The adsorption of water when plants are immersed by the incoming tide thus seems a likely mechanism of spore discharge. The similarities of unilocular reproductive structures and spore release in several brown algal species suggests common mechanisms of propagule discharge for members of thePhaeophyta.     

DEVELOPMENT OF ENDOPHYTIC FRANKIA SPORANGIA IN FIELD- AND LABORATORY-GROWN NODULES OF COMPTONIA PEREGRINA AND MYRICA GALE

Field-collected nodules of Comptonia peregrina (L.) Coult. and Myrica gale L. (Myricaceae), infected by the nitrogen-fixing actinomycete Frankia sp., were of two types: those that lacked sporangia entirely, designated spore(-), and those that showed extensive sporangial development, designated spore(+). In spore(+) nodules of C. peregrina, sporangia began to develop after the differentiation of endophytic vesicles and the concomitant onset of nitrogenase activity. At the onset of sporangial differentiation, infected host cells appeared healthy. However, endophytic vesicles and host cell cytoplasm and nuclei began to senesce rapidly as sporangia developed. Staining of sectioned material with the fluorescent stain Calcofluor White suggested that vesicles, hyphae and young sporangia were enclosed within a host-derived encapsulation layer, but mature sporangia were no longer encapsulated. In both C. peregrina and M. gale, vesicles were more short-lived in spore(+) than in spore(-) nodules. Field-collected spore(+) M. gale nodules exhibited a pronounced seasonality of sporangial formation. Sporangia began to differentiate in June, after the formation of vesicles and became more prominent in late summer. Inter- and intraspecific cross-inoculations suggest that the ability to form sporangia in the symbiotic state is controlled by endophytic strain type rather than host genotype or host/endophyte combination. The host may, however, influence the number and seasonal appearance of sporangia formed.     

Structural and physiological changes during sporangial development inAchlya intricata beneke

Summary Sporangial development in the zoosporic fungusAchlya intricata has been studied using light microscopy, a plasmolytic technique, KCl-filled microelectrodes and ion-selective microelectrodes. The completion of cleavage (spore delimitation) is accompanied by a change in appearance of the sporangium, loss of turgor and membrane potential, decrease in volume and release of K⁺. The measured loss of K⁺ is in agreement with previous measurements of extracellular ionic currents around developing sporangia ofAchlya using a vibrating probe. The relationship between these changes and the mechanism of spore liberation is discussed.     

SPORE MORPHOLOGY IN THE CYATHEACEAE. I. THE PERINE AND SPORANGIAL CAPACITY: GENERAL CONSIDERATIONS

The literature on cyatheaceous spore morphology relative to the presence of a perine layer is reviewed, and evidence based on a sodium-hydroxide assay is presented indicating that the outer scultpine layer in certain cyatheaceous spores is perine. Perine so defined characterizes Metaxya, paleotropical and certain neotropical species of Sphaeropteris, nearly all species of Alsophila, all species of Nephelea, and certain species of Trichipteris and Cyathea. It is lacking in Lophosoria, many species of Trichipteris and Cyathea, and all species of Cnemidaria. Two major patterns of spore number per sporangium in the family are reported. Lophosoria, Sphaeropteris, Trichipteris, Cyathea, Cnemidaria, and probably Metaxya are characterized by 64-spored sporangia, whereas most species of Alsophila and all species of Nephelea are characterized by 16-spored sporangia. The congruence of this generic distribution of sporangial-capacity types with Tryon's phyletic arrangement of cyatheaceous genera supports the naturalness of his system. The intrasporangial germination of spores retained in dehisced and dispersed sporangia supports the suggestion that decreased spore number per sporangium in Alsophila and Nephelea may relate to the role of the sporangia as dispersal units. The decreased number of spores per sporangium is associated with a trend toward increase in the number of sporangia per sores, with the highest known count approaching 1000 sporangia per sorus. The Alsophila-Nephelea evolutionary line has probably not been ancestral in the phylogeny of the more advanced groups of ferns.     

ACAULANGIUM GEN. N., A FERTILE MARATTIALEAN FROM THE UPPER PENNSYLVANIAN OF ILLINOIS

Material described by Graham as Cyathotrachus bulbaceus is believed to represent a new genus that is a common constituent of Upper Pennsylvanian coal balls. The sessile synangia of Acaulangium gen. n. are borne in a row on either side of the pinnule midrib and are composed of four to six short, tapering, laterally appressed sporangia. The sporangia have extended tips which curve over the inside of the synangium distally and delimit a small open area inside the synangium. The outer facing walls of the sporangia are two to three cells thick throughout while the inner facing walls are uniseriate. During dehiscence the sporangia separate laterally and spore release results from the rupture of a row of elongate cells along the inner sporangium midline. Among species of Scolecopteris the new genus resembles S. illinoensis and S. minor var. parvifolia but differs in its sessile synangial attachment. The additional parenchyma present between sporangial cavities in the synangia of Acaulangium, and the tendency toward bilateral symmetry suggests an early stage in the evolution of a bivalve synangium such as is present in Marattia.     

中华水韭孢子囊发育研究

采用半薄切片法,连续观察了极度濒危级(CR)植物中华水韭大小孢子囊的发育过程,以期从无性生殖的角度,为探讨其濒危原因提供直观可靠的理论根据。结果显示:(1)中华水韭的大小孢子叶相间排列,无混生孢子囊。(2)隔丝为孢子供给营养,其体积直接影响孢子的大小、产量和育性。(3)大小孢子囊都近半数败育,小孢子囊为整齐发育,大孢子囊为不整齐发育。(4)大小孢子囊均无柄,且都不存在开裂结构,只有孢子囊壁腐烂后才能散播孢子。研究认为,中华水韭的濒危与孢子囊的发育特征密切相关,孢子囊的高频率败育、没有开裂结构以及对环境的依赖,是造成中华水韭濒危的重要因素之一;通过与近缘类群孢子囊的比较,发现仅水韭孢子的散播借助外力,对生境要求较高,即验证了水韭古老的系统学地位,同时说明水韭更具有监测生境地区环境指标的能力。     

BOTRYOPTERIS PINNULES WITH ABAXIAL SPORANGIA

Small sporangia borne abaxially on pinnules attached to Botryopteris foliar members are described from coal ball petrifactions of Early Pennsylvanian age. This is the first report of laminar sporangia in this genus. Sporangia are stalked and borne singly near lateral veins on Sphenopteris-like pinnules. Individual sporangia are of the leptosporangiate type, with a lateral annulus and a dehiscence zone of thin-walled cells immediately adjacent to the annulus. Spores are small, trilete, triangular in outline, typically have blunt spines covering the exine, and correspond to the dispersed spore genera Acanthotriletes, Leiotriletes, or Lophotriletes. These sporangia and their spores are unlike previously described globose Botryopteris fructifications from the Middle and Upper Pennsylvanian, but are similar to sporangia produced by modern members of the Osmundaceae.     

Spores of microorganisms

The addition of penicillin (300–1,000 units/ml.) to a culture ofBacillus cereus during formation of the refractive prespores leads to lysis of the sporangia and to the release of spore components (calcium and dipicolinic acid) from the cells. Penicillin mildly raises the incorporation of amino acids, including diaminopimelic acid, into hot-TCA precipitate of cells, while chloramphenicol lowers it. In the later phases of penicillin inhibition, DAP-containing structures are also destroyed, including the fraction firmly bound to the envelope structures of the spore (in the control culture this fraction is not released until later, during digestion by enzymes localized in the envelope structures themselves). Penicillin inhibition of sporogenesis can be reversed by adapting the culture to penicillin or by simultaneously adding chloramphenicol. After the presporulation phase, sporogenesis is relatively resistant to chloramphenicol, but the whole process is considerably slowed down. Chloramphenicol also affects the morphology of the spores during their formation and inhibits their release from the sporangia until the late phase of sporulation.     

In vitro studies on the mechanisms of endospore release by Rhinosporidium seeberi

Studies of Rhinosporidium seeberi have demonstrated that this organism has a complex life cycle in infected tissues. Its in vivo life cycle is initiated with the release of endospores into a host's tissues from its spherical sporangia. However, little is known about the mechanisms of sporangium formation and endospore release since this pathogen is intractable to culture. We have studied the in vitro mechanisms of endospore release from viable R. seeberi's sporangia. It was found that watery substances visibly stimulates the mature sporangia of R. seeberi to the point of endospore discharge. The internal rearrangement of the endospores within the mature sporangia, the opening of an apical pore in R. seeberi's cell wall, and the active release of the endospores were the main features of this process. Only one pore per sporangium was observed. The finding of early stages of pore development in juvenile and intermediate sporangia suggested that its formation is genetically programed and that it is not a random process. The stimulation of R. seeberi's sporangia by water supports the epidemiological studies that had linked this pathogen with wet environments. It also explains, in part, its affinities for mucous membranes in infected hosts. The microscopic features of endospore discharge suggest a connection with organisms classified in the Kingdom Protoctista. This study strongly supports a recent finding that placed R. seeberi with organisms in the protoctistan Mesomycetozoa clade. This revised version was published online in June 2006 with corrections to the Cover Date.     

A Strategy for the Proliferation of Ulva prolifera,Main Causative Species of Green Tides,with Formation of Sporangia by Fragmentation

Ulva prolifera, a common green seaweed, is one of the causative species of green tides that occurred frequently along the shores of Qingdao in 2008 and had detrimental effects on the preparations for the 2008 Beijing Olympic Games sailing competition, since more than 30 percent of the area of the games was invaded. In view of the rapid accumulation of the vast biomass of floating U. prolifera in green tides, we investigated the formation of sporangia in disks of different diameters excised from U. prolifera, changes of the photosynthetic properties of cells during sporangia formation, and development of spores. The results suggested that disks less than 1.00 mm in diameter were optimal for the formation of sporangia, but there was a small amount of spore release in these. The highest percentage of area of spore release occurred in disks that were 2.50 mm in diameter. In contrast, sporangia were formed only at the cut edges of larger disks (3.00 mm, 3.50 mm, and 4.00 mm in diameter). Additionally, the majority of spores liberated from the disks appeared vigorous and developed successfully into new individuals. These results implied that fragments of the appropriate size from the U. prolifera thalli broken by a variety of factors via producing spores gave rise to the rapid proliferation of the seaweed under field conditions, which may be one of the most important factors to the rapid accumulation of the vast biomass of U. prolifera in the green tide that occurred in Qingdao, 2008.     

THE SPORANGIUM OF HORNEOPHYTON LIGNIERI (RHYNIOPHYTINA)

Numerous sporangia of Horneophyton lignieri from the Rhynie Chert locality in Scotland have been studied. The sporangia are branched, with two to four columellate lobes of varying length, and a continuous sporogenous zone or cavity occurs among the lobes. Unbranched sporangia, generally thought to be the typical form for the plant have not been found, and their presence is not established. Although not definitely proven, evidence suggests that the sporangia opened by means of a small apical pore or stoma. An area of thick-walled cells at the apex of each sporangial lobe probably played some role in this opening. Radial, trilete, azonate spores ranging from 39–49 μm in diam, with curvaturae perfectae are produced most commonly in tetrahedral tetrads and occasionally in isobilateral tetrads. Matters of spore preservation and possible ornamentation are discussed. The branched sporangia of this genus are unique among bryophytes and vascular plants and provide some evidence that certain synangia may have arisen from a single sporangium rather than from multiple sporangia borne singly at the tips of ultimate branches.     

A new group of Early Devonian plants with valvate sporangia containing sculptured permanent dyads

As part of a study to explore diversity and disparity in Early Devonian terrestrial vegetation, several hundreds of sporangia with in situ spores have been isolated from a Lochkovian locality in Shropshire. These include a small number (seven) of sporangia showing dehiscence into four valves and containing permanent sculptured dyads, belonging to the Cymbohilates horridus complex and C. cymosus, which are recorded in coeval dispersed spore assemblages. A further, previously described, mesofossil comprises an incomplete sporangium containing C. horridus that terminates a naked isotomously branching stem with stomata. The valvate sporangia are placed in a new genus, Partitatheca, containing four species, P. splendida (type), P. horrida, P. densa and P. cymosa, their names reflecting the names of the dispersed spore species and varieties. Complex ultrastructure in the walls of the dyads is similar to that in earlier dyads in the Dyadospora complex where it provides evidence for a hepatic affinity of the earliest embryophytes, but the new taxa present a combination of bryophyte and tracheophyte characters and are considered to represent a new embryophyte lineage. General discussion includes the development of dyads, more particularly their relevance to understanding the diversity in meiotic processes, and the disappearance of dyads from the dispersed spore record prior to the Middle Devonian. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 229–257.     

Development of the Mycetozoan Echinosteliopsis oligospora*

SYNOPSIS. The mycetozoan genus Echinosteliopsis, resembling the myxomycete Echinostelium in some of its features, is described. The single species, E. oligospora Reinhardt & Olive, forms small sporocarps which consist of a basal disk, stalk and a sporangium with only 1–8 spores. Spores form progressively, not simultaneously, by segmentation. The spores germinate to release non-flagellate amebae which, in liquid, assume a characteristic broad, fan shape. Each ameba has one or more nuclei. The nucleus is distinctive because of refractile, globular to elongate peripheral bodies which cytochemical tests indicate to be primarily RNA. At the time of nuclear division the characteristic RNA bodies disappear and, as observed with the phase microscope and in stained preparations, optically dense material accumulates in the middle area of the nucleus. Threads, either a spindle or actual chromatin, can be seen attached to the nuclear membrane. The threads separate to opposite poles as the nucleus elongates. During this division process the nuclear membrane apparently remains intact. Synchronous binucleate divisions, as well as a tripolar nuclear division, have been observed. Uninucleate and synchronous binucleate divisions may or may not be followed by cytokinesis. The absence of cell division after nuclear division leads to the production of cells with varying numbers of nuclei. Nuclear divisions in early sporangial stages and in spores have not been observed. The spores are uni- to multinucleate. In 8-spored sporangia and in most 4-spored sporangia there is a characteristic small “stalk spore” at the apex of the stalk. The stalk spore germinates slowly, if at all, but the larger spores germinate readily. No evidence of a sexual process has been found.     

STUDIES OF PALEOZOIC MARATTIALEANS: THE MORPHOLOGY AND PHYLOGENETIC POSITION OF EOANGIOPTERIS GOODII SP. N.

Eoangiopteris goodii sp. n. is described from Upper Pennsylvanian coal balls from Ohio (Shade locality) containing isolated pecopterid pinnules approx. 7 × 9 mm that bear up to 20 linear synangia on the lower surface. The synangia extend at right angles from the midrib to the downturned pinnule margins and measure 2.0–3.5 mm in length. Individual synangia are compact and are composed of 10–19 sporangia that have their bases embedded in an elongate parenchymatous pad. In longitudinal section sporangia measure 0.4 × 2.0 mm and have acute elongate, curved apices. Spores average 70 μm in diam and are most similar to the dispersed spore genus Verrucosisporites. Eoangiopteris goodii differs from the generitype E. andrewsii Mamay in its greater size, pinnule histology, and spore type. Sporangium wall complexity and spore type of the two presently known species of Eoangiopteris are considered to be at about the same evolutionary level as the more primitive species of Scolecopteris. Construction of the synangia in Eoangiopteris is different from that of Scolecopteris and indicates that at least two evolutionary lines are recognizable within the Pennsylvanian Marattiales.     

Induction of Accelerated Sporangial Lysis by Basic Peptide Antibiotics. A Novel Method of Preparation of Free Spores of Bacilli

An accelerated release of free spores from sporangia of Bacillus cereus NCIB-8122 and Bacillus subtilis SMYW was induced by the addition of the basic peptide antibiotics, polymyxin B or colistin (100 μg/ml), to sporangia formed in liquid Bactopeptone medium. Destruction of sporangial cell walls of B. cereus prelabelled with ³H-4-diaminopimelic acid commenced shortly after the addition of either antibiotic, the label being gradually released into the medium. Normal free spores were released following the addition of antibiotics to sporangia containing refractile spores (stages IV-V of sporogenesis). Earlier additions induced the lysis of both compartments of the sporangium, accompanied by the release of already-synthesized dipicolinic acid and alreadyaccumulated ⁴⁵calcium. The heat resistance and germination ability of spores released in the presence of the antibiotics were the same as those of control spores released by long-term spontaneous lysis of sporangia. Similar effects of the antibiotics were observed with B. subtilis SMYW. Results obtained were used firstly for fast preparation of relatively clean free spores and secondly for the characterization of the developmental stage of sporogenesis at which the spore becomes independent of the maternal cell. It reaches this property at the end of stage IV and during stage V.     

Rhinosporidium seeberi: Light,phase contrast,fluorescent and scanning electron microscopic study

Phase contrast microscopic study indicated the multilayered structure of the sporangial wall of R. seeberi while the scanning electronmicroscopic study revealed a trilaminated wall compared to a thick double walled light microscopic structure. The scanning electronmicroscopy revealed the spores of varying sizes which were found either discretely or in groups interconnected and seen attached to the inner aspect of the sporangial wall. Autofluorescence of sporangia and spores was observed under microscope. Acridine orange staining revealed the presence of DNA materials in the spore and sporangia.     

Observations on chytridiaceous parasites of Phanerogams

Summary A reexamination of Physoderma maculare Wallroth the type species of the genus, on Alisma, confirms Clinton's (1902) account of the production of an epibiotic stage from resting spore zoospores. The latter on mature host tissue may also give rise to the endobiotic stage which bears resting spores. On seedlings, however, resting spore zoospores produce only epibiotic sporangia. The fungus could not successfully infect Sagittaria, a closely related host.Contribution No. 1152     

SPORES OF BOTRYOPTERIS GLOBOSA AND BOTRYOPTERIS AMERICANA FROM THE PENNSYLVANIAN

A study of spores from fertile pinnae of Botryopteris from middle and upper Pennsylvanian coal balls from Iowa, Illinois, and Kansas indicates that there are two distinct species, Botryopteris globosa and B. americana. The organization and attachments of fertile pinnae and the sporangial morphology and dimorphism are identical in the two species. Data are given on fertile pinnae dimensions, attachments of six fertile pinnae, spore counts from individual sporangia, and spore morphology. The ornamentation of B. americana spores is verrucate to rugulate with verrucae fusing to a variable extent to form bars and convolute ridges; B. globosa spores are vermiculate or fossulate to densely rugulate with scattered verrucae. Comparisons are made with B. forensis and a re-interpretation of the spore forms of B. forensis is suggested.     

The sporangia of Horneophyton lignieri (Kidston and Lang) Barghoorn and Darrah

Two sporangia of Horneophyton lignieri are described in greater detail from new material collected from the Rhynie locality. The sporangia are branched repeatedly, with up to three successive dichotomies, resulting in five columellate lobes with a continuous spore cavity. Dehiscence is by a slit at the apex of each sporangial lobe. Stomata occur on tips of emergences in the sporangial wall.