Morphological and cytological investigations ofUlothrix zonata and taxonomy of the related species

The present communication deals with the observations made on the morphology, reproduction and cytology ofUlothrix zonata (Weber & Mohr)Kütz. in culture. The alga displays a remarkable phenotypic plasticity in nature as well as in culture. The present study provides additional evidence of karyology in support ofLokhorst andVroman's treatment ofU. zonata which merges a number of earlier described species in it. The cytological details and chromosome number (n = 10) determined for the Indian isolates ofU. zonata agree with those ofSarma for the British material.NBRI Research Publication No. 63 (N.S.)     

Morphological variation and taxonomy of thePoa macrocalyx complex (Poaceae) in Hokkaido

Morphological features of 41 local populations of thePoa macrocalyx complex from the seasides of Hokkaido were analyzed with special reference to the following seven characters: spikelet length, number of florets per spikelet, relative length of side nerves to the entire length of the first glume, that of the second glume, length ratio of the second glume to a spikelet, ratio of length of the closed part vs. entire length of leaf sheaths, and scabrousness of panicle branches and pedicels. All of these characters varied continuously, and considerable degrees of variability within a population were observed. However, separation of populations into three groups became evident when the data were subjected to principal component analysis and also to a method of examination which was devised for identification of a population (not an individual) of this complex. The three groups that resulted from morphological studies were exactly in parallel with the grouping of populations supported by differences of chromosome numbers and geographical distribution. Evolutionary differentiation of this complex was discussed in connection with polyploidy and gametophytic apomixis. As a result of taxonomic considerations, the plants were arranged in three emended varieties of one species:Poa macrocalyx var.fallax, P. m. var.tatewakiana, P.m. var.scabriflora.     

气-水两生型丝孢真菌的多样性与分类研究

气-水两生型真菌通常定植于自然森林生态系统中溪流或池塘沉积的腐枝叶上,菌丝生长于水体底部,当沉积物暴露于空气中时,形成分生孢子并发育成中空的孢子繁殖体,使其能漂浮在水面,附着新的基质,进行生长繁殖。世界范围内已报道约20属116种,大多为无性型的丝孢菌,其独特的生存环境和产孢特点,在真菌的形态、生态和系统演化上有重要研究价值。文中主要从多样性和分类学、采集与分离培养、孢子形态和发育、有性型-无性型关系、系统演化关系等方面对其进行了综述,为该类真菌系统的研究及潜在的应用提供参考。     

Hyphomycetes from Nigerian rain forests

Phaeobotrys gen. nov., based on Phaeodactylium acutisporum, characterized by branched and pigmented conidiophores, and the production of hyaline, appendiculate conidia from denticles on polyblastic conidiogenous cells which usually extend sympodially to form more conidiogenous loci, and Zanclospora stellata sp. nov., recognized by its stellate sterile branches in the distal part of the conidiophore and bacilliform conidia, are described and illustrated from decaying leaf litter from Nigeria. Keys to Phaeobotrys and related genera, and to species of Zanclospora are proposed. Furthermore, a list of hyphomycetes newly reported for Nigeria is provided.     

Hyphomycetes in the River Kelvin

Summary

The hyphomycete spora of the River Kelvin and its tributary, the Allander Water, was sampled during October 1986 to January 1987. Twenty spore types were found, the commonest being Flagellospora curvula and Lemonniera aquatica. Spore numbers were high in October and declined during the autumn to an undetectable level by the end of December, but leaves collected in December and January yielded spores on incubation in water.     

Effects of Cadmium on Aquatic Hyphomycetes

Two kinds of experiments, sporulation and growth experiments, were carried out to demonstrate the effect of cadmium on aquatic hyphomycetes. Oak (Quercus petraea L.) leaves were exposed in a hard-water stream (Lüssel, Swiss Jura) and a soft-water stream (Ibach, Black Forest) for 2 months. In the laboratory, fungal sporulation on the leaves in stream water enriched with cadmium (as CdCl₂) was studied. A measurable effect was found when the cadmium concentration exceeded 0.1 ppm (0.1 mg/liter). Concentrations higher than 100 ppm inhibited conidium production completely. This toxic effect of cadmium was species dependent and much higher in soft water (water with low concentrations of calcium and magnesium) than in hard water. Growth experiments with Alatospora acuminata Ingold, Clavariopsis aquatica De Wildeman, Flagellospora curvula Ingold, Heliscus lugdunensis Saccardo and Therry, and Tetracladium marchalianum De Wildeman showed the same pattern of cadmium sensitivity as that seen in the sporulation experiments. Mycelial growth was less sensitive to cadmium than was fungal sporulation. High concentrations of competing cations (e.g., calcium and zinc) or potential ligands could reduce cadmium toxicity. Calcium content seems to be the most important factor responsible for the different sensitivity of aquatic hyphomycetes in hard and soft water.     

Temperature and Sporulation of Aquatic Hyphomycetes

Temperature appears to be an important factor affecting the occurrence and distribution of aquatic hyphomycetes, the dominant leaf litter-decomposing fungi in streams. We compared conidium production by eight species of aquatic hyphomycetes grown on yellow poplar leaves in stream-simulating microcosms at three temperatures (15, 20, and 25°C). The greatest conidium production occurred at 15°C for one species, 20°C for two species, and 25°C for two species. Two species produced similar numbers of conidia at 20 and 25°C, and one species produced similar numbers of conidia at all three temperatures. Linear growth rates were determined on malt extract agar. Six species had the same pattern of temperature responses for growth on malt extract agar as for sporulation on leaves, as shown by the positive correlations between the two parameters at the three temperatures. The species examined also exhibited differences in number of conidia produced from a similar amount of leaf material at a given temperature. These differences appeared to be due primarily to differences in individual conidium mass (determined by weighing conidia produced from cultures), as shown by the relationship of the type Y = k/X (r² = 0.96), where Y is the number of conidia produced, X is the individual conidium mass in milligrams, and k is a constant empirically determined to be 2.11. This finding supports the hypothesis that aquatic hyphomycetes allocate similar amounts of their resources to reproduction but vary with respect how these resources are partitioned into reproductive units (conidia).     

Ergosterol-to-Biomass Conversion Factors for Aquatic Hyphomycetes

Fourteen strains of aquatic hyphomycete species that are common on decaying leaves in running waters were grown in liquid culture and analyzed for total ergosterol contents. Media included an aqueous extract from senescent alder leaves, a malt extract broth, and a glucose-mineral salt solution. Concentrations of ergosterol in fungal mycelium ranged from 2.3 to 11.5 mg/g of dry mass. The overall average was 5.5 mg/g. Differences among both species and growth media were highly significant but followed no systematic pattern. Stationary-phase mycelium had ergosterol contents 10 to 12% lower or higher than mycelium harvested during the growth phase, but these differences were only significant for one of four species examined. Availability of plant sterols in the growth medium had no clear effect on ergosterol concentrations in two species tested. To convert ergosterol contents determined in field samples to biomass values of aquatic hyphomycetes, a general multiplicative factor of 182 is proposed. More accurate estimates would be obtained with species-specific factors. Using these in combination with estimates of the proportion of the dominant species in a naturally established community on leaves resulted in biomass estimates that were typically 20% lower than those obtained with the general conversion factor. Improvements of estimates with species-specific factors may be limited, however, by intraspecific variability in fungal ergosterol content.     

New species ofEdmundmasonia (Hyphomycetes)

A new species ofEdmundmasonia Subram,E. villosa is illustrated and described from decaying culms of bamboo collected in Cuba. Two others, which are Indian species, are briefly discussed.     

Morphological variability, taxonomy, and distribution of Cyclotella bodanica Eulenstein (Bacillariophyta) in Russia

The morphology of six populations of a rare freshwater species of diatoms, Cyclotella bodanica Eulenstein, from lakes of different geographic location is studied using SEM techniques. It is shown that some features (number of striae and marginal fultoportulae in 10 μm, number of thin costae in alveoli and their branching, relief of the central area and peripheral zone, and arrangement of rimoportulae) vary to a greater extent than is indicated in the literature. The results have made it possible to improve the diagnosis of this species and refer C. intermedia to its synonymy. Similarities and differences between C. bodanica and morphologically similar species of the complex C. comta/C. radiosa are also considered. The distribution of C. bodanica in water bodies of Russia is specified.     

Interesting dematiaceous Hyphomycetes on Lodoiceamaldivica dead fragments

Two new species, Virgariella lodoicea and Cacumisporium oceanicum and a new record of Diplocladiella scalaroides from Seychelles islands are proposed. A species of Helicosporium which could not be determined is also described.     

Hyphozyma,a new genus of yeast-like Hyphomycetes

Hyphozyma gen. nov. is characterized by pink, slimy colonies, showing initial-or late-stage budding and hyphae which produce conidia in basipetal succession through inconspicuous lateral openings. The cell walls contain rhamnose. Two species and a variety are described and their relation to some genera of yeasts and Hyphomycetes is discussed.     

丝孢真菌无性与有性进化分析

绝大多数丝孢真菌属、种主要以无性型存在,但该类真菌绝大多数属、种含有若干调控有性分化、发育及进化的基因信息,如交配型、信息素及G-蛋白α-亚基基因等,胁迫环境诱导这些真菌有性基因有效表达乃至发育为有性型,一直倍受真菌学界的关注。文中系统介绍了丝孢真菌无性型与有性型属种分类研究现状、进化分析及性别调控基因,1)分析属、种三类有性基因的多样性、异型交配基因比率、系统发育关系及有性进化潜力与趋势;2)分析属、种不同有性基因调控特性胁迫环境适应性,界定靶标基因及适宜生态因子,结合地球生境演化特性,预测属、种自然演化性别变化动态;3)分析靶标基因调控生态,阐明两性种有性基因调控生态遗传机制。综上有望解析绝大多数丝孢真菌属、种主要为无性型的本质原因,丰富丝孢真菌分类研究的理论,为真菌分类研究提供科学依据。