Cell wall metabolism during fruiting of the basidiomycete Schizophyllum commune

During the development of fruit bodies of the basidiomycete Schizophyllum commune, the alkali-insoluble (R glucan) and alkali-soluble (S glucan) cell wall fractions are synthesized during the entire course of morphogenesis. The water soluble glucan (WSG) is not synthesized after an early stage. There is also a relative increase in the proportion of S glucan during development which appears related to a change in the proportion of the components synthesized. Data are also presented to show that several fruiting mutants also have specific cell wall differences, and that there is a significant contribution to cell wall structure by genes which do not cause a macroscopically observable change in phenotype.     

Factors affecting fruit set in Aizoaceae species of the Succulent Karoo

By reducing the number of flowers and fruits, intense grazing activities of domestic livestock are considered to have negative effects on the plant recruitment of perennial plants in the Succulent Karoo, South Africa. In the present study, the fruit set of six perennial species belonging to the Aizoaceae was investigated under two different grazing intensities. Two species (Cheiridopsis imitans and Leipoldtia schultzei) were examined more closely to determine whether factors other than grazing impact fruit production of these plants. Apart from reproductive output, the population structure of these two species was explored in heavily and slightly grazed areas.For all investigated species, heavy livestock grazing was identified as a major threat to fruit production. Deviations from this pattern were recorded in a drought year, when harsh weather conditions reduced herd sizes dramatically and the usually high grazing pressure was alleviated. However, detailed analyses revealed that also other biotic factors can cause severe fruit and flower losses even exceeding that caused by grazing. Caterpillars of the noctuid moth, Diaphone eumela, and two rodent species, Otomys unisulcatus and Rhabdomys pumilio, proved to be further important herbivores of flowers and fruits. Experiments with caged plants, excluding livestock from grazing, confirmed though that livestock grazing definitely accounts for a continuous reduction of fruit production. Insufficient pollination success was another parameter reducing fruit set; however, this was almost exclusively observed under low grazing pressure.     

Factors affecting the proportion of sterile soldiers in growing aphid colonies

The proportion of sterile soldiers in an aphid colony is positively correlated with colony size. Assuming logistic growth of the aphid colony, Aoki and Kurosu (Insect Soc 50:256–261, 2003) presented an inequality that determines, for any colony size, whether a soldier or a reproductive will be added to the colony. To put it in words, if the marginal defensive efficacy of a soldier, multiplied by the number of reproductives, is larger than the mean productivity of reproductives without defense by that soldier, the soldier will be produced; if not, a reproductive will be produced. Based on Aoki and Kurosus inequality, we carried out simulations to determine whether the proportion of soldiers increased with colony size. Given a constant level of depredation per aphid and a constant number of predators, proportion of soldiers continued to increase with colony size unless a single soldier was very effective or unless carrying capacity was very large. Given a constant number of nongluttonous predators and a decreasing level of depredation per aphid, proportion of soldiers soon began to decrease after a peak. However, given an increasing number of nongluttonous predators to keep a constant level of depredation per aphid, proportion of soldiers again continued to increase. These results confirmed the argument that the proportion of soldiers can increase with colony size under a wide range of realistic assumptions.     

Behavioral testing of antidepressant compounds: an analysis of crossover design for correlated binary data

The differential reinforcement of low-rate 72 seconds schedule (DRL-72) is a standard behavioral test procedure for screening potential antidepressant compounds. The protocol for the DRL-72 experiment, proposed by Evenden et al. (1993), consists of using a crossover design for the experiment and one-way ANOVA for the statistical analysis. In this paper we discuss the choice of several crossover designs for the DRL-72 experiment and propose to estimate the treatment effects using either generalized linear mixed models (GLMM) or generalized estimating equation (GEE) models for clustered binary data.     

The control of fruiting body formation in the ascomycete Sordaria macrospora Auersw. by regulation of hyphal development

The morphological effects of biotin and L-arginine on fruiting body formation of the ascomycete Sordaria macrospora are investigated by scanning electron and light microscopy. Biotin is recognized as an elongation factor and arginine as a branching factor in vegetative and reproductive hyphae. In the absence of exogenous biotin, development is blocked after the ascogonium-core hypha stage of protoperithecial morphogenesis, whereas linear growth of the myceliar front is maintained. The addition of exogenous arginine to a biotin deficient culture induces the formation of numerous side branches even in the older mycelium. Fruiting body formation, however, remains blocked at the protoperithecial stage as before, because of the inability of the side branches to elongate. When biotin and arginine are administered simultaneously, a most vigorous branching and growth are induced in the older mycelium, accompanied by a rapid and maximal formation of fruiting bodies. The results are summarized in a model of the exogenous control of hyphal morphogenesis. The model is designed to explain the relationship between fruiting and hyphal density as well as the edge effect on fruiting body formation.     

Factors affecting the occurrence and distribution of entomopathogenic fungi in natural and cultivated soils

Factors affecting the occurrence and distribution of entomopathogenic fungi in 244 soil samples collected from natural and cultivated areas in Spain were studied using an integrated approach based on univariate and multivariate analyses. Entomopathogenic fungi were isolated from 175 of the 244 (71.7 %) soil samples, with only two species found, Beauveria bassiana and Metarhizium anisopliae. Of the 244 soil samples, 104 yielded B. bassiana (42.6 %), 18 yielded M. anisopliae (7.3 %), and 53 soil samples (21.7 %) harboured both fungi. Log-linear models indicated no significant effect of habitat on the occurrence of B. bassiana, but a strong association between M. anisopliae and soils from cultivated habitats, particularly field crops. Also, irrespective of habitat type, B. bassiana predominated over M. anisopliae in soils with a higher clay content, higher pH, and lower organic matter content. Logistic regression analyses showed that pH and clay content were predictive variables for the occurrence of B. bassiana, whereas organic matter content was the predictive variable for M. anisopliae. Also, latitude and longitude predicted the occurrence of these same species, but in opposite directions. Altitude was found to be predictive for the occurrence of B. bassiana. Using principal component analysis, four factors (1 to 4) accounted for 86 % of the total variance; 32.8, 22.9, 19.6 and 10.4 % of the cumulative variance explained, respectively. Factor 1 was associated with high positive weights for soil clay and silt content and high negative weights for soil sand content. Factor 2 was associated with high positive weights for soil organic matter content and high negative weights for soil pH. Factor 3 was associated with high positive weights for latitude and longitude of the sampled localities and factor 4, had high positive weights only for the altitude. Bi-plot displays representing soil samples were developed for different factor combinations and indicated that, irrespective of geographical location, absence of both fungal species was determined by alkaline sandy soils with low organic matter content, whereas heaviness of soil texture, acidity and increasing organic matter content led to progressively higher percentages of samples harbouring entomopathogenic fungi. These results could aid decision-making as to whether or not a particular cultivated or natural soil is suitable for using entomopathogenic fungi as a pest control measure and for selecting the fungal species best suited to a particular soil.     

Factors affecting transformation of cell cultures from three dicotyledonous pigment-producing species using microprojectile bombardment

Gene transfer methods were established for cell suspension cultures of sweet potato (Ipomoea batatas), ohelo (Vaccinium pahalae) and carrot (Daucus carota, two lines) using micro-projectile bombardment. Several parameters were studied (particle size/type, helium pressure, stage height, DNA concentration, pre-culture period) to determine which significantly affected transformation efficiency. All the physical parameters influenced transient gene expression, with particle size and type having the greatest effect. Cell culture age also affected transformation efficiency in all cell lines. Nuclear DNA conformation (relaxation) as measured by flow cytometry showed no change associated with culture age or transformation efficiency. Agrobacterium-based methods were also tested and in most experiments produced no GUS-expressing loci. Microprojectile bombardment will now be used to study anthocyanin biosynthesis in cell cultures as an alternative source of natural food colourants.     

Factors affecting the survival and growth of bacteria introduced into lake water

The populations of Pseudomonas sp. B4, Escherichia coli, Klebsiella pneumoniae, Micrococcus flavus, and Rhizobium leguminosarum biovar phaseoli declined rapidly in lake water. The initially rapid decline of the two pseudomonads and R. phaseoli was followed by a period of slow loss of viability, but viable cells of the other species were not found after 10 days. The rapid initial phase of decline was not a result of Bdellovibrio spp., bacteriophages, or toxins in the water since Bdellovibrio spp. were not present and passage of the lake water through filters that should not have removed bacteriophages or soluble toxins led to the elimination of the rapid phase of decline. The addition of 250 g of cycloheximide and 30 g of nystatin per ml eliminated viable protozoa form the lake water, and the population of Pseudomonas sp. B4 did not fall and the decline of E. coli and K. pneumoniae was delayed or slowed under these conditions. Pseudomonas sp. L2 proliferated rapidly in lake water amended with glucose, phosphate, and NH₄NO₃, but its numbers subsequently fell abruptly; however, in water amended with cycloheximide and nystatin, which killed indigenous protozoa, the population density was higher and the fall in numbers was delayed. Of the nutrients, the chief response was to carbon, but when glucose was added, phosphorus and nitrogen stimulated growth further. Removing other bacteria by filtering the lake water before inoculation with Pseudomonas sp. L2 suggested that competition reduced the extent of response of the pseudomonad to added nutrients. We suggest that the decline in lake water of bacteria that are resistant to starvation may be a result of protozoan grazing and that the extent of growth of introduced species may be limited by the supply of available carbon and sometimes of nitrogen and phosphorus, and by predation by indigenous protozoa.     

Factors affecting calculation of nutritional induces for foliage-fed insects: an experimental approach

To determine how nutritional indices for insects fed leaves are affected by the experimental conditions and the physiology of the plant material, we used larvae of the buckmoth, Hemileuca lucina Hy. Ed. (Saturniidae) and their hostplant Spiraea latifolia Ait. Bork (Rosaceae). Under experimental conditions identical to those used to determine larval nutritional indices, we found that the age of leaves (new versus mature) significantly affected their metabolism and water loss, but simulated herbivory did not directly affect leaf metabolism. Over a 6-day test, nitrogen concentration showed an initial increase followed by a gradual decline, and was higher in new leaves compared to mature leaves. New leaves increased in protein concentration and then gradually returned to the initial level, whereas mature leaves changed little over the 6-day test. These changes in percent nitrogen and protein may largely reflect the disproportional changes in non-nitrogenous materials. Solitary and grouped larvae had similar growth rates on new leaves, but they differed on mature leaves. Deliberate manipulation of larvae during the course of an experiment significantly reduced relative growth rates by increasing duration of the stadium rather than by decreasing biomass gained. Two methods of estimating larval gut contents at mid-stadium were compared: weight of frass produced and weight of digestive tract and contents. After the end of the 4-day test period used to determine nutritional indices, the digestive tracts with food accounted for 10.8% of the larval dry weight. Larval frass produced in 24 h after the end of the test period comprised 9.3% of the larval dry weight. Correction factors for plant metabolism changed nutritional indices by 1 to 8%, while those for larval gut contents altered indices by 2 to 15%.     

Factors affecting the distribution of a predatory mite on greenhouse sweet pepper

The predatory mite Neoseiulus cucumeris is used for biological control of phytophagous mites and thrips on greenhouse cucumber and sweet pepper. In a previous study, N. cucumeris provided effective control of broad mite but was only rarely found on the sampled leaves, raising questions about the factors affecting N. cucumeris distribution. To determine the distribution of N. cucumeris, leaves of pepper plants were sampled three times per day: just after sunrise, at noon and just before sunset for two years and throughout a 24 h period in one year. The presence of other mites and insects was recorded. Biotic (pollen) and abiotic (temperature, humidity) factors were monitored from the three plant levels. The effect of direct and indirect sunlight on the mites was assessed. N. cucumeris was found primarily in flowers; however, the mite’s distribution was affected by other predators (intraguild predation); in the presence of the predatory bug Orius laevigatus virtually no mites occurred in the flowers. Whereas temperature and humidity varied from the top to the lower level of the plants, apparently neither these factors nor the presence of pollen outside the flowers influenced mite distribution. N. cucumeris was found to be negatively phototropic; therefore N. cucumeris were pre-conditioned to light by rearing under light conditions for 4 months before being released. The light-reared mites were initially more numerous during the noon sampling period, however, rearing conditions caused only a temporary and non-significant change in distribution.     

MOBCENTR: A nonhierarchical classification algorithm for exploratory data analysis (EDA)

MOBCENTR is a classification algorithm combining features of classification about mobile centres, Ward algorithm and of the Hard-Isodata method. The results of this new algorithm and of Ward algorithm are compared by morphological characters of species ofSolidago andPimpinella.     

Factors affecting protoplast yield of the carrageenophyte Solieria filiformis (Gigartinales,Rhodophyta)

Summary The effect of age, pH of the culture medium, pre-treatment of tissues, enzymes sources and enzymatic adaptability of phycophages fed with a monospecific diet were analyzed on the protoplast yields of the red seaweed Solieria filiformis (Kützing) Gabrielson. New apices from fast growing plants showed the highest protoplast yields. The protoplast yield decreased when the pH of the culture medium increased from 6.0 to 9.0. Crude extracts from the abalone Haliotis coccinea canariensis Nordsieck, fed with Solieria filiformis thalli for three months in combination with cellulysin, released the highest number of viable cells and protoplasts. Yields ranged from 1.0 to 8.5 x 10⁶ protoplasts per gram of fresh weight.Abbreviations AAP abalone acetone powder - Bis-Tris Bis(2hydroxyethyl)imino-tris(hydroxymethyl)methane - CMC carboxymethyl cellulose - EDTA ethylenediaminetetraacetic acid - EGTA ethylene glycol-bis(ß-aminoethyl ether) NNNN-tetraacetic acid - FDA fluorescein diacetate - FW fresh weight - Hepes N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - Tris Tris(hydroxymethyl)aminomethane     

Factors affecting the excision frequency of the maize transposable element Ds in Arabidopsis thaliana

A two-element transposon system based on the maize elements Ac and Ds is currently being used for insertional mutagenesis in Arabidopsis. With the aim of making this system as efficient as possible we have continued to analyse several parameters which affect Ds activity in Arabidopsis. The influence of genomic position on Ds excision has been analysed in five lines carrying Ds integrated in different genomic locations. Differences in both somatic and germinal excision were observed between the different lines. The relationship between somatic and germinal excision, the timing of excision events and environmental influences on transposition frequency have been investigated. The effect of varying dosage of the different elements was also analysed. A strong positive dosage effect was observed for the transposase source, but not for the Ds element. Analysis of germinal excision events showed that the majority of them occurred very late in the development of the plant, resulting in the majority of Ds transpositions being independent events.     

Factors affecting immigration of adults: experimental and theoretical observations with rodents

We examined immigration in populations of Peromyscus leucopus (white-footed mice) by 1) monitoring natural immigration at 10 sites, 2) introducing experimental immigrants into eight populations, and 3) constructing qualitative models of immigration. Density of natural immigrants covaried positively with resident density, and successful assimilation was lower at low resident and immigrant densities. Females and males did not differ in their chance of achieving residency. Year, sex, and number introduced were significant predictors of assimilation by individuals. Experimentally introduced individuals had no effect on densities of those mice resident before the introductions. Results obtained from studying natural immigration differed from those obtained from studying experimental immigration. Signed digraphs and time averaging were used to model the consequences of different resident-immigrant relationships and to suggest how different sources of variation may have affected assimilation and led to differences in natural and experimental immigration. Resident and immigrant densities could have been positively correlated even if residents actively inhibited immigration. Variation in immigrant density and survival rather than resident territorial activity apparently determined patterns of assimilation.     

Generic interrelationships of theCardueae (Compositae): A cladistic analysis of morphological data

A cladistic analysis of 45 genera ofCardueae for 75 characters is presented, taking into account characters of bracts, corolla, stamens, styles and cypselas. Forty-six binary characters completeBremer's (1994) work. Some of the characters considered byBremer are criticised. The traditionalCarlininae is a paraphyletic group, the ten genera studied sharing no common derived character. A new classification of theCardueae is proposed and the distribution of the tribe is presented. Several new combinations are proposed. The nomenclature ofCentaurea is discussed and the status of the genusSerratula is analysed.     

Factors affecting the glucosylation capacity of cell cultures of Datura innoxia and Scopolia carniolica for monophenolic compounds

Suspension grown cells of Datura innoxia and Scopolia carniolica were tested for their glucosylation capacity and some factors affecting the efficiency of the reaction were studied.Cells at the end of the exponential growth phase showed a high glucosylation capacity. Light conditions had little effect on the bioconversion reaction. For the substrates hydroquinone and p-hydroxybenzoic acid the bioconversions were concentration-dependent. Permeabilization with propanol diminished the bioconversion capacity. Depending on the substrate used, relatively large amounts of substrate and product could not be recovered. Tannic acid could partly prevent decomposition of the compounds. The bioconversion capacity of cultures with a low glucosylation capacity could be enhanced by addition of uridine diphosphate-glucose, indicating that the sugar donor is a critical factor. From six substrates the natural compounds hydroquinone, p-hydroxybenzoic acid and vanillin were glucosylated. No glucosides were detected from tyramin and two synthetic aminotetralines.Abbreviations 5HAT 5-hydroxyaminotetralin - NO437 2-(N-propyl-N-2-thienylamino)-5-hydroxytetraline - pHBA p-hydroxybenzoic acid - UDP-glucose uridine diphosphate-glucose