Interaction between two synthetic pyrethroids and the spread of two non-persistent viruses in cowpea

The effectiveness of the synthetic pyrethroids deltamethrin and lambda-cyhal-othrin in preventing (i) aphid colonisation of four cowpea cultivars with different levels of aphid resistance and (ii) the introduction and subsequent spread of cowpea aphid-borne mosaic virus and cucumber mosaic virus was investigated under tropical field conditions. Sprays of these pyrethroids eight days apart prevent aphid colonisation and within crop spread of virus by the colonising Aphis craccivora. However, neither deltamethrin nor lambda-cyhalothrin prevented the initial introduction of virus into the cowpea crop and, when incoming alate incidence was high, virus incidence was higher in the sprayed than in the unsprayed plots. In addition, the degree of aphid resistance of each cultivar affected secondary virus spread within the crop, with greatest spread in the most resistant cultivar.     

Toxicity of Sodium and Chloride Ions to Rhizobium spp. in Broth and Peat Culture

The growth of a strain of Rhizobium trifolii and of R. meliloti was studied in broth and peat cultures to determine the relative toxicity of Na⁺ and Cl^-. The following salts were added in a range of concentrations: Na₂HPO₄ as a source of Na⁺, CaCl₂.2H₂O as a source of Cl^-, and NaCl. Disodium hydrogen orthophosphate affected the growth rate of both strains in broth culture but not in peat culture. Unexpectedly, calcium chloride was more toxic than NaCl in broth and peat culture. The toxicity of NaCl can be ascribed to the Cl^-. Rhizobium meliloti strains grew on 3·5% NaCl after adaptation during a long period. Rhizobia for soya bean and cowpea grew at 0·5% NaCl and those for clover and pea, at 1·0% NaCl.     

Cell Expansion and Wall pH in the Fern Regnellidium diphyllum, A Plant Lacking Acidinduced Growth

Petioles of the semi-aquatic fern Regnellidium diphyllum donot show acid growth but low wall pH is a necessary conditionfor maximum rates of IAA-induced cell expansion. Measurementsof wall pH by two indirect methods indicate an unusually lowvalue, in the range pH 4 to 5. This is one to two pH units belowthat estimated for petioles of the semi-aquatic dicotyledonNymphoides peltata, a species in which IAA aand ethylene causegrowth responses very similar to those in Regnellidium but whereacid growth occurs. Having shown previously that fusicoccinenhances proton secretion in both Regnellidium and Nymphoides,we now show that although it causes a reduction in the estimatedapoplast pH to below 4·0 in Regnellidium, cell expansionis not promoted. The FC-induced reduction in pH in Nymphoidesis less and occurs more slowly, but growth is promoted significantly;when IAA and fusicoccin are present together, growth promotionis approximately additive for Nymphoides A model is proposed for Regnellidium in which equilibrium wallpH is maintained at a low value that is optimal for acid growth,the availability of acid-labile sites in the wall being thechief limitation to cell extension. We suggest that this controlmechanism may be widespread for organs without a cuticle, includingroots and the gametophytes of lower plants growing in acidicconditions. Key words: Acid growth, wall pH, fusicoccin, Regnellidium diphyllum, Nymphoides peltata     

The Relationship of Fixed Carbon and Nitrogen Sources to the Greening Process in Euglena gracilis strain Z*

SYNOPSIS The pattern of chloroplast development was followed in Euglena gracilis strain Z greening in media with a variety of fixed carbon and nitrogen sources. The greening pattern of cells grown in inorganic medium with added ethanol or glucose involves an inhibition of chloroplast development when compared to that of cells grown in inorganic medium alone. Several nitrogen sources were tested to ascertain their effectiveness in relieving the inhibition of chloroplast development by glucose. Of those, only 0.05% (w/v) (NH₄)₂ SO₄ accelerated the recovery from the inhibition after most of the glucose had been removed from the medium by the cells. The other nitrogen sources tested were not effective. An inhibition of chloroplast development, similar to that observed in cells greening in the presence of glucose, was seen in cells greening in an ethanol-containing medium. These cells, however, had a different response upon the addition of 0.05% (NH₄)₂ SO₄. They appeared to recover from the inhibition of chloroplast development, even before the ethanol was removed from the medium by the cells. A slight enhancement of chloroplast development was noted in cells greening in an inorganic medium with glycine or serine. Other amino acids tested had little or no effect.     

The relationship between invertebrate assemblages and available food at forest and pasture sites in three southeastern Australian streams

1. Levels of ash-free dry matter (AFDM) and chlorophyll a in epilithon, benthic participate organic matter (BPOM), invertebrate assemblage composition, and biomass of functional feeding groups were compared in winter and summer at forest and pasture sites in three Victorian streams. 2. Chlorophyll a concentrations of epilithon were significantly higher at pasture than forest sites in winter but not in summer while BPOM was not significantly greater at forest sites in either season. Epilithic biomass as AFDM did not show consistent differences between land uses or seasons. 3. Total biomass of invertebrates did not differ between forest and pasture sites but the biomass of shredders was significantly higher, and that of grazers significantly lower, at forest than pasture sites. A site shaded with an artificial canopy behaved as a forest site for grazers but as a pasture site for shredders. 4. Cluster analyses of invertebrate assemblages grouped pasture sites with forest sites on the same stream at the same season, indicating that assemblage composition was less influenced by land-use differences than by between-stream and seasonal differences. 5. Biomass of functional feeding groups appeared to be a more sensitive indicator of invertebrate assemblage response to land-use alteration than either species diversity/ richness measures, or multivariate assemblage composition measures.     

Modelling habitat selection of Common Cranes Grus grus wintering in Portugal using multiple logistic regression

Predictive models of habitat suitability for the Common Crane Grus grus in a wintering area of southern Portugal were derived using logistic multiple regression and Geographic Information Systems. The study area was characterized by landscape variables and surveyed uniformly for the presence of cranes. The most important variables were distance to roosts, to open Holm Oak woods and to villages, and the occurrence of unpaved roads, shrubby vegetation, slope and orchards. Two models were built, the second having one variable fewer than the first. The selection of the best model was based on statistical and biological criteria. Crane distribution was negatively related to: distance to open Holm Oak Quercus rotundifolia woods and roosts. Additionally, unsuitable vegetation and orchard areas are avoided. In these areas movement is difficult, food availability is reduced and the risk of predation increased. We also found that villages and roads were avoided; disturbance is a significant factor for this species. Some management guidelines are proposed for the area: (1) maintenance of open Holm Oak woodlands, (2) incentives to avoid the abandonment of traditional agriculture and pastoral use of the area, which would lead to an increase of shrubby vegetation areas, (3) preservation of suitable roosting places and (4) management of new patches of forest and orchards.     

MtPM25 is an atypical hydrophobic late embryogenesis‐abundant protein that dissociates cold and desiccation‐aggregated proteins

Late embryogenesis‐abundant (LEA) proteins are one of the components involved in desiccation tolerance (DT) by maintaining cellular structures in the dry state. Among them, MtPM25, a member of the group 5 is specifically associated with DT in Medicago truncatula seeds. Its function is unknown and its classification as a LEA protein remains elusive. Here, evidence is provided that MtPM25 is a hydrophobic, intrinsically disordered protein that shares the characteristics of canonical LEA proteins. Screening protective activities by testing various substrates against freezing, heating and drying indicates that MtPM25 is unable to protect membranes but able to prevent aggregation of proteins during stress. Prevention of aggregation was also found for the water soluble proteome of desiccation‐sensitive radicles. This inhibition was significantly higher than that of MtEM6, one of the most hydrophilic LEA protein associated with DT. Moreover, when added after the stress treatment, MtPM25 is able to rapidly dissolve aggregates in a non‐specific manner. Sorption isotherms show that when it is unstructured, MtPM25 absorbs up to threefold more water than MtEM6. MtPM25 is likely to act as a protective molecule during drying and plays an additional role as a repair mechanism compared with other LEA proteins.     

Variations in Expression of Markers by Populations of Adherent Cells from Trypanosoma cruzi-Infected Mice1

The kinetics of differentiation and maturation of phagocytic cells during the acute and chronic stages of experimental Chagas' disease was examined by monitoring changes in expression of peroxidase (PO), nonspecific esterase (NSE), C3b receptors (CR), Fc receptors (FcR), and phagocytic ability of cells in the blood, spleen, and peritoneal cavity. The significant changes recorded in the blood were: marked increases in the percentages of CR- and FcR-positive adherent cells during both the acute and chronic phase; Ia-positive cells increased two-fold in the acute period and remained elevated in the chronic stage. In the spleen, the major alterations recorded during both the acute and chronic stages were: two- to three-fold increases in the percentages of NSE- and PO-positive adherent cells and three- to four-fold increases in the proportions of CR- and FcR-positive cells. In addition, Ia-positive cells increased from 70% to approximately 90% of the adherent cell population. In the peritoneal cavity, a two- to four-fold elevation in the percentages of both PO- and NSE-positive cells was observed. The number of Ia-positive cells increased from 10% before infection to 85–90% during the acute phase and to 96–98% during the chronic period. All of the changes described above occurred in the absence of noticeable increases in phagocytic ability except for an elevation in the percentage of circulating latex-ingesting cells seen during chronicity. These results indicate that infection with Trypanosoma cruzi alters the pathways of differentiation of cells of the mononuclear phagocyte lineage.     

Genome-wide Analysis of Transcript Abundance and Translation in Arabidopsis Seedlings Subjected to Oxygen Deprivation

Annals of Botany 96: 647–660, 2005 Unfortunately, there were errors in Figure 5 of this article.The     

PLANT MITOSIS PROMOTING FACTOR DISASSEMBLES THE MICROTUBULE PREPROPHASE BAND AND ACCELERATES PROPHASE PROGRESSION IN TRADESCANTIA

The regulation of mitosis in higher plant cells has been investigated by microinjecting protein kinase from the metaphase-arresting (met1) mutant ofChlamydomonas. Biochemical characterization of this enzyme complex confirms the presence of a p34^cdc2/cyclin B-like kinase. The enzyme was injected into living stamen hair cells ofTradescantia virginianain which microtubules (MTs) were visualized using fluorescent analogue cytochemistry and confocal laser scanning microscopy. Microinjection of this p34^cdc2/cyclin B-like kinase caused rapid disassembly of the preprophase band of MTs but not of interphase-cortical, spindle or phragmoplast MTs. Effects of the enzyme on the cytomorphology of live prophase cells were also monitored using video microscopy. We found that injection of this enzyme accelerated chromatin condensation and nuclear envelope breakdown. This indicates the presence and function in plants of an enzyme that can initiate nuclear division similar to the maturation or mitosis promoting factor (MPF) of animal cells. These studies provide the first direct evidence that the mitotically-active form of plant MPF can drive disassembly of preprophase band MTs, chromosome condensation and initiation of mitosis in plant cells.