Structural properties of two types of mangrove stands on the northwestern coast of Sri Lanka

Mangrove stands in Puttalam lagoon and Dutch bay, two interconnected lagoons situated on the northwestern coast of Sri Lanka have been classified broadly into two groups, i.e., estuarine and island/mainland-fringing stands. Structural diversity of six mangrove stands, representing the two types was studied in terms of floristic composition, density, basal area, mean stand diameter, tree height, standing above-ground biomass and leaf-area index.Rhizophora mucronata andAvicennia marina were the dominant species. Higher mean stand diameters for the mangrove stands in Puttalam lagoon indicated greater maturity than the estuarine mangrove stands in Dutch bay. Nevertheless, estuarine stands in Dutch bay were structurally more complex (complexity indices 8.11–22.7) than the island/mainland-fringing mangrove stands (complexity indices 1.38–6.78). Higher number of species present in the estuarine mangrove stands is the major element that contributes to the higher values for the complexity indices for those stands. This appears to mask the contribution of stand-age to the complexity of a mangrove stand. Therefore complexity indices alone may not be used to explain adequately the structural diversity among mangrove stands.     

Structure and species distribution in Coringa mangrove forest,Godavari Delta,Andhra Pradesh,India

Coringa mangrove forest is located in the Godavari delta, Andhra Pradesh, India. The mangrove community consisted of more than 13 species of mangrove and other plants in the present study area. The following three dominant mangrove plants,Avicennia marina, Excoecaria agallocha andSonneratia apetala were found to be present on the banks of a major channel of the Godavari river running through the forest. The structure and species distribution of mangrove, in the Channel Nagathana Kalaya has been described. The area behind the belt consisting ofAcanthus ilicifolius andMyriostachya wightiana is generally colonized byE. agallocha andA. marina. The zone has been called theAvicennia andExcoecaria zone. Adjacent to this zone species likeAegiceras corniculatum andA. officinalis were the common species. In the flat clayey soil,Suaeda maritima was found to grow. In areas of high elevation, devoid of inundation of tidal seawater during the high tidal period, species such asM. wightiana andAcanthus were found to colonize both the banks of the channels.An analysis of species diversity, indicated a definite trend in the distribution of mangrove from the mouth of the estuarine region to the inland waters.The levels of atmospheric pollutants such as sulphur dioxide (SO₂), oxides of nitrogen (NO_x), ammonia (NH₃) and suspended particle matter (SPM) were within the legal limits.     

Fungi from decaying intertidal fronds of Nypa fruticans, including three new genera and four new species

HYDE, K. D., 1992. Fungi from decaying fronds of Nypa fruticans, including three new genera and four new species. Decaying fronds and exposed stems of the mangrove palm Nypa fruticans were collected from beaches and intertidal regions of mangroves in Brunei and examined for the presence of higher marine fungi. Forty-three species were identified, four of which are new to science. The fungi included 32 Ascomycotina, one Basidiomycotina and ten Deuteromycotina. Three new genera and four new species are described and illustrated.     

Impact of salinity stress on soil-borne fungi of sugarbeet

The sugarbeet cultivar Kaumera was found to be highly susceptible to infection by the root-rot pathogens Rhizoctonia solani and Sclerotium rolfsii in the absence of salinity stress. Under this environmental condition, R. solani was more efficient than S. rolfsii in producing cell wall-degrading enzymes in infected hypocotyls. Xylanase and galactanase were most effective. The rate of cell wall degradation by R. solani was nearly 2.5 times that of S. rolfsii when cells walls of healthy hypocotyls were used as sole carbon substrate for the in vitro produced crude enzymes.Under salinity stress the pathogenicity and the performance of cell wall-degrading enzymes of R. solani and S. rolfsii varied profoundly. Pathogenicity studies showed that R. solani appeared to be more tolerant than S. rolfsii of the salinity stresses applied, and relatively more virulent to cv Kaumera. The activities of cell wall enzymes of R. solani decreased and those of S. rolfsii increased with increased salt concentration when cell wall material was used as a sole carbon source. The metabolic products produced under salinity stress by R. solani and R. solani in the cell wall amended culture media shifted the initial pH towards neutrality or slight alkalinity for R. solani and to high acidity for S. rolfsii.When model substrates were used, xyland and galactan were the most responsive substrates for degradation by the cell wall enzymes of the two fungi studied. The rate of degradation was higher for S. rolfsii than for R. solani. The excessive acidity in salt stressed S. rolfsii culture media suggested reduced activities of the enzymes involved in cell wall degradation in vivo. This may explain the decreased virulence potentialities.     

The vacuolar ATPase ofNeurospora crassa

The filamentous fungusNeurospora crassa has many small vacuoles which, like mammalian lysosomes, contain hydrolytic enzymes. They also store large amounts of phosphate and basic amino acids. To generate an acidic interior and to drive the transport of small molecules, the vacuolar membranes are densely studded with a proton-pumping ATPase. The vacuolar ATPase is a large enzyme, composed of 8–10 subunits. These subunits are arranged into two sectors, a complex of peripheral subunits called V₁ and an integral membrane complex called V₀. Genes encoding three of the subunits have been isolated.vma-1 andvma-2 encode polypeptides homologous to the and subunits of F-type ATPases. These subunits appear to contain the sites of ATP binding and hydrolysis.vma-3 encodes a highly hydrophobic polypeptide homologous to the proteolipid subunit of vacuolar ATPases from other organisms. This subunit may form part of the proton-containing pathway through the membrane. We have examined the structures of the genes and attempted to inactivate them.     

Association of soybean root mycoflora with root modulation, root necrosis and plant fresh weight

Fungi were isolated from soybean plants in ten fields in south-west France. Correspondence analysis (COA) was used to find associations among taxa (species, genera, groups) and sampling units (i.e. one field at one sampling date). The first axis of the COA demonstrated a dominant sampling date effect; the second indicated an association among certain sampling units and specific taxa. Regression analysis of COA coordinate values indicated that fields with high relative isolation frequencies of Fusarium spp., F. oxysporum and ‘other species’ (mostly Chaetomium spp. and sterile fungi) were characterised by greater plant fresh weight and nodule number and lower ratings for root necrosis. Cylindrocarpon spp., Cephalosporium spp. and F. solanihad high relative isolation frequencies in fields with lower plant weight, lower nodule number and higher root necrosis ratings. The relative importance of fungal taxa was also related to soil type.     

Bioenergetic consequences of glucoamylase production in carbon-limited chemostat cultures ofAspergillus niger

Aspergillus niger has been grown in glucose- and maltose-limited continuous cultures to determine the bioenergetic consequences of the production of the extracellular enzyme glucoamylase. Growth yields (g biomass per mol substrate) were high, indicating that growth was very efficient and protein production for biomass was not exceedingly energy consuming. It has been found that the energy costs for the production of this extracellular enzyme is very high. Depending on the efficiency of energy conservation the glucoamylase protein yield on ATP is between 1.3 and 2.6 g protein per mol ATP, which is equal or less than 10% of the theoretical maximum of 25.5. These high energy costs most probably have to be invested in the process of excretion. A comparison between an industrial over-producing strain and the wild typeAspergillus niger showed that this over-producing strain most probably is a regulatory mutant. Two regions of specific growth rates could be determined (one at specific growth rates lower and one at specific growth rates higher than 0.1 h^-1), which are characterized by differences in mycelium morphology and a significant deviation from linearity in the linear equation for substrate utilization. Analysis of the region of specific growth rates higher than 0.1 h^-1 yielded maintenance requirements of virtual zero. It has been concluded that for a good analysis of the growth behaviour of filamentour fungi the linear equation for substrate utilization is not suitable, since it contains no term for the process of differentiation.     

Spatial patterns and sampling plans for cereal aphids [Hom.: Aphididae] killed by entomophthoralean fungi and hymenopterous parasitoids in spring wheat

Cereal aphids infesting spring wheat in southwestern Idaho were surveyed during 1988 and 1989 for the presence of entomophthoralean fungi and hymenopterous parasitoids. Cereal aphids killed by the fungi (cadavers) and parasitoids (mummies) includedDiuraphis noxia (Mordvilko),Metopolophium dirhodum (Walker),Sitobion avenae (F.), andSchizaphis graminum (Rondani). Taylor's power law was used to describe the relationships between mean densities of cadavers or mummies (number per tiller) and associated variances. Except forS. graminum mummies, which were at low levels throughout the growing seasons and tended to be randomly distributed, Taylor's slopes exceeded 1.0 for all the aphid cadavers and mummies, indicating varying degrees of clumping in spatial pattern. The spatial patterns ofD. noxia andM. dirhodum cadavers were similar, simply reflecting those of their own populations, but more aggregated than were their respective mummies resulting from parasitoid attack. The intercepts and slopes from the power law analysis were used to generate functional relationships between the proportion of wheat tillers bearing cadavers or mummies of each aphid species and the mean density, and develop optimal numerical (direct counting) and binomial (presence or absence) sample size curves for both cadavers and mummies of each aphid species.      

Temporal relationships betweenZea mays,ostrinia nubilalis (Lep.: Pyralidae) and endophyticBeauveria bassiana

The entomopathogenic fungus,Beauveria bassiana (Balsamo) Vuillemin, was applied to whorl-stage (V7) corn,Zea mays L., by foliar application of a granular formulation of corn grits containing conidia or by injection of a conidial suspension. All plants were infested with European corn borer larvae,Ostrinia nubilalis (Hübner), at the V7 (whorl), V12 (late-whorl), or V17 (pretassel) stage of plant development. Plants infested at whorl and late-whorl stages had significantly more European corn borer tunneling than did plants infested at the pretassel stage. The percentage of plants colonized byB. bassiana did not differ significantly among the whorl, late-whorl, and pretassel stages. As the plants matured,B. bassiana was isolated from different plant areas, with the pith more frequently colonized than the leaf collars. Foliar application ofB. bassiana provided immediate suppression ofO. nubilalis in those plants infested at whorl stage. The reduced efficacy ofB. bassiana at the intermediate plant stages relative to efficacy at harvest is discussed. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

青藏高原东缘的锈菌资料I.竹上的柄锈菌一新种

描述了采自四川西部山区竹上的柄锈菌一新种,即寄生在箭竹Sinarundinaria nitida(Mitf.) Nakai上的箭竹柄锈菌Puccinia sinarundinariae J-y. Zhuang & S.-x. Wei。模式标本保藏在中国科学院微生物研究所真菌标本室。