The action of some systemic aphicides on the nymphs of Anthocoris nemorum (L.) and A. confusus Reut

The aphicides phorate, dimethoate and menazon were compared to elucidate the different pathways by which they can affect Anthocoris nymphs and their aphid prey.
When nymphs were caged in contact with deposits on bean leaves phorate and dimethoate had contact LC 50s of 20 and 3 μg/cm² respectively to Anthocoris nemorum and 46 and 6 μg/cm² to A. confusus. When the nymphs were confined on treated leaves on the opposite surface to the deposits, neither phorate nor dimethoate killed them. Menazon did not kill anthocorids at any dosage. All three aphicides killed over 50% of Acyrthosiphon pisum (Kalt.) on bean leaves at 1.6 μg/cm² whether the aphids were on the treated or untreated surface.
Experiments with ³⁵S-labelled phorate showed that anthocorids confined on phorate-treated bean plants, with or without insect food, accumulated the insecticide or its labelled derivatives. In field experiments in which A. nemorum were caged on plants treated with phorate, many were killed on young newly treated plants but not on older plants. A. confusus was relatively unaffected.
Anthocorids were reared from 2nd-instar nymphs to adults on aphids killed systemically with phorate, dimethoate or menazon without ill effects, despite evidence that ³⁵S-labelled phorate was ingested from the aphids and excreted in the faeces.
In the field, fewer large A. nemorum nymphs were found in August in plots of tick beans treated with phorate granules at 6 lb/acre (6.7 kg/ha) when sown, than in plots treated at 1.5 lb/acre (1.7 kg/ha) with phorate or menazon or untreated plots.     

Multiplication of Pseudomonas syringae pv. phaseolicola"in planta"

In the compatible combination of the halo blight disease of bean Pseudomonas phaseolicola was able to colonize large areas of the intercellular space of leaves, such that these confluent water congested areas became visible as water-soaked spots. Most of the plant cell walls in the infected region maintained their normal shape, even when the cytoplasm had collapsed. Some inward bending of plant cell walls preceded their rather slow degradation and final replacement by bacterial masses. Neighbouring plant cells appeared to be metabolically active. In resistant leaves no indications of active bacterial attachment or encapsulation could be observed. However, bacteria appeared to be more densely packed in resistant leaves, and relatively more plant cells completely collapsed as compared with susceptible leaves. From 8—14 days after inoculation, the bacterial concentration did not change much in susceptible or resistant leaves, indicating the absence of bactericidal components. Even Pseudomonas pisi snowed some multiplication in bean leaves (immune reaction), but its growth stopped earlier than that of P. phaseolicola. in the resistant cultivars, probably due to a different mechanism of resistance. Although less bacteria were determined in the intercellular washing fluid (IF) compared with leaf homogenates, the high bacterial concentrations in the IF supported our observation that an effective encapsulation of bacteria in resistant leaves did not occur.     

Influence of continuous challenge via the feed on competitive exclusion of salmonellas from broiler chicks

A survey has been made of the bacterial and fungal populations carried at three different sites on the feet of 60 individuals. The bacteria found at the three sites were quantitatively similar and Micrococcaceae and aerobic coryneform bacteria predominated. The carriage of other bacterial groups was generally low. There was a quantitative variation between sites—mean total counts were 1.04 ± 10⁷ cfu/cm² skin in the fourth toe cleft, 4.08 ± 10⁵ cfu/cm² skin on the sole and 1.21 ± 10³ cfu/cm² skin on the dorsal surface. Staphylococci were most often dominant on the sole and dorsal surface whereas aerobic coryneforms predominated in the majority of fourth toe clefts. The higher the total count at a given site the more likely it was that aerobic coryneform bacteria predominated. The skin surface pH was significantly higher on the sole (mean value 6.25) than on the dorsal surface (mean value 5.23). Factors controlling the microbial ecology of the foot are discussed.     

Translocation of selenium in the bean plant (Phaseolus vulgaris) and the field bean (Vicia faba)

Selenium distribution in the bean plant ( Phaseolus vulgaris L. cv. Contender) was studied using autoradiographs of the whole plant and of sections of organs. A few hours after the incubation of the roots with (⁷⁵Se) selenate, a major part of the selenate accumulates in the roots, while the fraction conveyed towards the aerial organs is unevenly distributed, resulting in accumulation of ⁷⁵Se in the young leaves, the buds and the epicotyl. This distribution results from a general translocation of selenium through the xylem. A secondary process of redistribution is then immediately linked to the transport of ⁷⁵Se labeled products (such as seleno-amino acids) in the phloem from the mature leaves. A similar pattern of translocation of selenium was found in the field bean ( Vicia faba L. cv. Aguadulce) by using aphids that insert their stylets into the sieve tubes. Measurement of the radioactivity of these insects shows that the ⁷⁵Se content of the phloem sap was reduced to low levels when all the mature leaves were excised. The mature leaves thus serve as relaying organs, redistributing the selenium which is carried in by the movement of water through the xylem.     

The use of direct epifluorescent microscopy (DEM) and the direct epifluorescent filter technique (DEFT) to assess microbial populations on food contact surfaces

Two rapid methods, direct epifluorescent microscopy (DEM) and the direct epifluorescent filter technique (DEFT) on swab resuspension fluids, were compared with the traditional total viable count (TVC) on swab resuspension fluids for their ability to enumerate surface populations of attached bacteria. The degree of error in estimating surface populations was shown to be significantly less with DEM than DEFT followed by TVC. DEM estimated populations in the range 3 times 10³ to 5 times 10⁷ colonies/cm² whilst DEFT enumerated populations above 3 times 10⁴ colonies/cm² and TVC above 3 times 10⁵ colonies/cm² (as measured by DEM). Swabbing was shown to remove a constant proportion of organisms from the surface populations tested, although below 3 times 10⁵ colonies/cm² most of the organisms remained in the cotton matrix and were difficult to resuspend. DEFT was more able to enumerate swab resuspension fluids obtained from surface populations below 3 times 10⁵ colonies/cm² than was TVC.     

A novel terrestrial halophilic environment: The phylloplane of Atriplex halimus, a salt-excreting plant

Abstract This paper describes the microbial ecosystem found on the leaves of Atriplex halimus , a salt-excreting plant in the central Negev highlands of Israel. Because of the regular nightly occurence of dew at this location, these leaves undergo a diurnal wetting so that phylloplane microorganisms experience large fluctuations in salinity and water activity, as well as tolerate repeated desiccation. During the dry season, in the late spring and summer, a significant amount of salts and organic material coats the leaf surface. During dew events the salt concentration at the leaf surface was calculated to be > 0.4 M. Direct counts of the respiring bacteria on the leaf surface ranged from 1.06×10⁴ to 5.06×10⁵ per cm². Using a variety of media it was shown that there was limited bacterial diversity which could be cultured, with greater than 90% of the isolates being orange colored Gram-negative rods. Viable counts ranged from 0.32 to 2.32×10⁴ bacteria per cm² of A. halimus leaf surface. No bacteria capable of nucleating ice were recovered in these studies. The dominant orange pigmented bacterium, identified as a halotolerant Pseudomonas sp., grew optimally at 30°C and at 5% NaCl and was capable of growth in media containing up to 20% NaCl. This bacterium could grow on a variety of organic compounds, including some associated with plant materials. The leaf bacteria were desiccation-tolerant when on the leaf surface or when directly washed off the leaves, but much less so when in isolatd culture. A major component of the tolerance to desiccation is probably related to the compounds on the leaf surface.     

Transport and redistribution of selenium in the bean plant (Phaseolus vulgaris)

After incubation for 3 h with (⁷⁵Se) selenate, the selenium distribution in the bean plant (Phaseolus vulgaris L. cv. Contender) through a 29-day period showed an uneven distribution: roots and trifoliate leaves were richer in ⁷⁵Se than stem and primary leaves. The high selenium concentration of roots resulted from the retention of selenate by the root cells: at the end of the 29-day period about 60° of the radioactivity was always ethanol-soluble, and when analysed by paper chromatography, proved to be selenate. By contrast, much of the radioactivity of the leaves was ethanol-insoluble, ⁷⁵Se being quickly captured in metabolic processes which immobilize it. During plant development, a portion of the total selenium remains mobile and is continually mobilized to the younger organs which display a rapid growth rate. This delivery results from a progressive liberation of selenate retained by mature organs, especially the roots, and from turnover in older leaf tissues, especially the trifoliate leaves.     

Mediation of sterol-induced calmodulin synthesis in Phaseolus vulgaris roots by Ca2+ and its possible relationship to plant growth regulators

Vitamin D₃ and stigmasterol have been previously shown to stimulate growth, Ca²⁺ fluxes and calmodulin synthesis in Phaseolus vulgaris roots. In this study, these sterols (10⁻⁹ M ) were shown to accelerate the incorporation of [³H]-thymidine into DNA in Phaseolus vulgaris (L. cv. Contraancha) root apices, similarly to a mixture of the mitogenic plant growth factors 2,4-dichlorophenoxyacetic acid and kinetin (4.6 μ M each). The effects of stigmasterol were blocked by flufenazine, a calmodulin antagonist. Analogously to stigmasterol, the plant hormones stimulated calmodulin synthesis as shown by double labeling of root proteins with [¹⁴C]-leucine and [³H]-leucine, respectively, followed by their separation on sodium dodecyl sulfate-po-lyacrylamide gels and a calmodulin affinity column, immunoblot analysis and cyclic AMP phosphodiesterase activation assays. The stimulation of root calmodulin formation by stigmasterol was abolished in the absence of Ca²⁺ in the incubation medium and was mimicked by the Ca²⁺ ionophore A–23187. The results suggest that the sterols, like plant mitogenic hormones, promote DNA synthesis, and that these compounds stimulate calmodulin synthesis as a consequence of their mitogenic activity. ^Ca2+ appears to mediate the action of the sterols.     

The inhibition of photosynthesis and photorespiration in isolated mesophyll cells of Phaseolus and Lycopersicon by reduced osmotic potentials

Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by ¹⁴CO₂ release in CO₂-free air and by ¹⁴CO₂ release from the oxidation of [1–¹⁴C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO₂ compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I⁻¹1 at −1.08 MPa to 130 μl 1⁻¹ for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non- stomatal inhibition of CO₂ assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure.     

Inheritance of Anthracnose Resistance in the Common Bean Differential Cultivar G 2333 and Identification of a New Molecular Marker Linked to the Co-42 gene

The inheritance of anthracnose resistance of the common bean ( Phaseolus vulgaris L.) differential cultivar G 2333 to Colletotrichum lindemuthianum races 73 and 89 was studied in crosses with the susceptible cultivar Rudá. The segregation ratios of 15 : 1 in the F₂ and 3 : 1 in the backcrosses to Rudá indicate that for each of the races tested there are two independent resistance loci in G 2333. A random amplified polymorphic DNA (RAPD) molecular marker (OPH18_1200C) linked in resistance to race 73 was identified in a BC₃F_2:3 population derived from crosses between Rudá and G 2333. A RAPD molecular marker OPAS13_950C, previously identified as linked to gene Co-4² , was also amplified in this population. Co-segregation analyses showed that these two markers are located at 5.6 (OPH18_1200C) and 11.2 (OPAS13_950C) cM of the Co-4² gene. These markers were not present in BC₁F_2:3 plants resistant to race 89 indicating that this population carries a different resistance gene. DNA amplification of BC₁F_2:3 plants with RAPD molecular marker OPAB_450C, previously identified as linked to gene Co-5 , indicated that this gene is present in this population.     

Bacterial Counts and Quality of Iced Fish Retailed at a Lusaka Market, Zambia

S ummary . The counts of total viable, coliform, streptococcal and sulphite reducing anaerobic bacteria and the presence of salmonellae were determined on 134 iced fish obtained from Luburma Market, Lusaka, Zambia, during June-December 1970. The quality of the uncooked fish was also assessed by appearance and odour. The purpose of these determinations was to obtain a picture of the variations of the bacterial counts in relation to season, origin, fish species and market quality. Total viable and coliform counts were of the order of millions and tens of thousands/cm² of skin surface, respectively. Higher counts were obtained in the hot season during September-October but with little change in appearance of the fish. There was a significant correlation ( P < 0·01) of both total viable and coliform bacteria with quality scores. A maximum permissible level of 10⁷ cells/cm² of skin surface was proposed for total viable counts and 10⁵/cm² for coliform bacteria, for iced fish of acceptable quality in Zambia.     

Ion supply capacity of roots in relation to rejuvenation of primary leaves in vivo

Removal of the shoot above the primary node (detopping) of 3-week-old bean plants ( Phaseolus vulgaris L. cv. Contender) altered the metabolism and development of the remaining leaves. An increase in levels of chlorophyll, protein, stomatal opening, photosynthesis and growth, i.e. rejuvenation of primary leaves, was established within 7 days of detopping. These levels were maintained while the primary leaves of equivalent intact plants senesced.
The flux of xylem solution (mineral ions, cytokinins and water) into leaves is related to the leaf area to be supplied and root supply capacity; it has been suggested that detopping leads to an increased availability of root-supplied solutes and hence rejuvenation of the remaining leaves. This assumes however that root output of solutes is not decreased by the defoliation treatment.
We found that root output of ions (electrical conductivity of passive xylem exudate) in detopped plants was 30% lower than in intact plants after 24 h and 60% lower after 7 days. The output of Ca²⁺, Mg²⁺ and K⁺ were similarly reduced 7 and 14 days after detopping as were fresh and dry weights of roots. Furthermore, neither the calculated xylem flux of ions nor directly measured levels of Ca²⁺, Mg²⁺ and K⁺ were significantly increased in leaves of detopped plants during their rejuvenation. We therefore conclude that root output is tightly coupled to shoot demand and that the apparent rejuvenation of primary leaves caused by detopping bean plants is not a consequence of increased xylem flux of mineral ions into the leaves.     

On the mechanism of rejuvenation of ageing detached bean leaves by low-concentration stressors

The effect of low concentrations of some stress-inducing compounds of different toxicity and chemical nature, such as Cd and Pb salts or DCMU, was investigated on the senescence of chloroplasts in detached primary leaves of bean ( Phaseolus vulgaris L . ). After 1 week of senescence followed by root development from the petiole, these agents stimulated chlorophyll accumulation and photosynthetic activity (¹⁴CO₂ fixation) as compared to the control, thus inducing rejuvenation. Low-concentration stressors increased the level of active cytokinins in roots and leaves during the treatment, as monitored by the Amaranthus betacyanin bioassay and high-pressure liquid chromatography. The lithium ion, an inhibitor of the PIP₂-IP₃/DAG signal transduction pathway, abolished the stimulating effect of stressors, both in roots (retarding cytokinin synthesis) and consequently also in leaves (reducing cytokinin-dependent chlorophyll accumulation). This suggests the involvement of the PIP₂-IP₃/DAG signal transduction pathway in generation of these consecutive organ-specific responses.     

A note on the use of 3-section plates for the estimation of the numbers of bacteria and to obtain isolated colonies in 1 day

By streaking with an open loop and then swabbing a 4–5 cm² area on 3-section agar plates, it is possible to obtain isolated colonies and to estimate bacterial densities from 100 to 10⁷/ml on the swabbed area.     

Vitamin D3 affects growth and Ca2+ uptake by Phaseolus vulgaris roots cultured in vitro

Vitamin D₃ at low concentration (10⁻⁹ M) inhibited the growth of Phaseolus vulgaris L. (cv. Contrancha) roots in vitro as measured by elongation (14 h) and [³H]-leucine incorporation into protein (2 h), and increased their labelling with ⁴⁵Ca²⁺ (2 h). Cycloheximide and puromycin (50 u.M) blocked vitamin D₃ stimulation of root ⁴⁵Ca²⁺ labelling, indicating that it is mediated by de novo protein synthesis. The calcium ionophore X-537A (10⁻⁵JW) induced similar changes both in root elongation and ⁴⁵Ca²⁺ uptake (14 h). This may indicate that the inhibitory effects of the sterol on root growth are mediated by changes in Ca²⁺ fluxes. However, this interpretation should be further strengthened by additional studies as the ionophore may have acted on root growth, affecting physiological processes other than Ca²⁺ transport.     

Fusicoccin-induced membrane depolarization, K+ efflux and extracellular alkalinization in leaves of Vigna unguiculata

Abstract. In leaves of three different cultivars of cowpeas ( Vigna unguiculata ), the fungal toxin fusi-coccin (FC) induced a plasmalemma depolarization from -175 to -100mV, a value slightly below the N₂-determined diffusion potential in the dark, and to a lesser extent in the light. The depolarization was preceded by the usual initial membrane hyperpolarization (up to 18mV). The membrane depolarization was accompanied by considerable K⁺ efflux and extracellular alkalinization. Primary and secondary leaves as well as stem tissue of plants, grown under long-day conditions or in the dark responded similarly. Dark O₂ uptake in leaves and hypocotyls was stimulated by FC by up to 77 and 87%, respectively. In contrast, FC caused a typical E_m hyperpolarization, K⁺ influx, extracellular acidification and smaller stimulation of respiration (50%) in leaves of other legumes such as mungbean ( Vigna radiata ), or soybean ( Glycine max ). Leaves of navy beans ( Phaseolus vulgaris ) revealed an intermediate response to FC. The unusual effect of FC in Vigna might be related to the production of toxic catabolites during degradation and fermentation of storage products necessary to meet the strong energy requirement of the pm-H⁺ ATPase.     

Long-term effects of low levels of SO2 on bean plants (Phaseolus vulgaris). II. Immission-response effects on biomass production: quantity and quality

Bean plants ( Phaseolus vulgaris L. cv. Processer) were grown in water culture with separate air supply to roots for four to five weeks at five levels of SO₂ ranging from 10 μg m⁻³ to 950 μg m⁻³. At harvest the plant material was divided into six fractions: root, stem, fruit and leaves of three age groups.
Plants were mainly affected at and above approx. 250 μg m⁻³ SO₂. Fresh weight was reduced in mature and old leaves, and roots and fruit. Dry weight was also reduced in mature and old leaves, and roots and stem. A reduction was found in chlorophyll a and chlorophyll b in mature and old leaves, and also starch was reduced in the leaves. Sulfur content of leaves and fruit increased with exposure time and concentration, while Br, Ca, Cl, K, Mn, P and Zn increased at the highest SO₂ level only. Total (but not specific) peroxidase activity increased in all aerial fractions, i.e. soluble protein increased just like peroxidase activity. Seventeen studied amino acids all increased on the average by 38% in mature bean pods.
The observed effects may be parts of a reaction for survival and propagation of the plant, as fruit quality was not affected, indeed, it sometimes improved slightly. The latter observation is of commercial interest.     

Effect of K+ and H+ stress and role of Ca2+ in the regulation of intracellular K+ concentration in mung bean roots

The effects of external K⁺, H⁺ and Ca2⁺ concentrations on the intracellular K+ concentration, [K⁺]i, and the K⁺-ATPase activity in 2-day-old mung bean roots [ Vigna mungo (L.) Hepper] were investigated. [K⁺]i, in mung bean roots was markedly decreased by external K⁺ or H⁺ stress and did not recover the initial value even after the stress was removed. This decrease in [K⁺]i, gradually disappeared with the addition of (Ca2⁺. Ca2⁺ may offset the harmful effects of ion stress. Ca2⁺ seems to have two effects on K+ transport; control of K⁺ permeability and activation of K⁺ uptake, although K⁺-ATPase activity was inhibited by Ca2⁺ concentrations higher than 10–4 M. We suggest that Ca2⁺ activates K⁺ uptake indirectly through the acidification of the cytoplasm.     

EVALUATION OF ADENOSINE TRIPHOSPHATE (ATP) BIOLUMINESCENCE FOR ESTIMATING BACTERIA ON SURFACES OF BEEF CARCASSES

A rapid (<15 min), inexpensive and simple method has been developed to estimate the concentration of bacteria on surfaces of beef carcasses using adenosine triphosphate (ATP) bioluminescence. Surfaces (5x5 cm²) of beef carcasses (n= 159) were collected by excision. An ATP assay and aerobic plate count were performed on each sample. A significant (p < 0.001) positive linear relationship (r = 0.83) between plate count and ATP assay was obtained for 159 beef carcass samples. When thresholds levels were set at 1 × 10⁴, 1 × 10⁵ and 1 × 10⁶ CFU/cm², there was moderate to good agreement between the ATP bioluminescence assay and the aerobic plate count as determined by the k-statistic. The application of this ATP bioluminescence test to HACCP systems for beef slaughter processes is discussed.     

The cloning and characterization of phage promoters, directing high expression of luciferase in Pseudomonas syringae pv. phaseolicola, allowing single cell and microcolony detection

Regions of DNA containing promoter sequences from a Pseudomonas syringae pv. phaseolicola -specific phage (φ11P) were identified by shotgun cloning into a broad-host-range promoter-probe vector (pQF70). When used in conjunction with the luciferase reporter genes, one of these DNA fragments, 19H, directed gene expression at a level which enabled the subsequent light output (bioluminescence) of single cells of P. syringae pv. phaseolicola to be detected and visualized using a charge-coupled device (CCD). The P. syringae pv. phaseolicola φ11P, 19H and P. aeruginosa φPLS27, HcM promoters gave a 50-fold increase in bioluminescence (maximum relative light output) compared to similar constructs containing other well-characterized promoters, for example, tetracycline. Similar bioluminescent characteristics of the transformed bacterium, were observed during growth with and without antibiotic-selection. When lux ⁺ bacteria were inoculated onto French bean leaf ( Phaseolus vulgaris L.), the resultant secondary halo blight lesions were bioluminescent and during phylloplane colonization by the lux ⁺ bacterium, bioluminescence on leaf surfaces was detected and imaged by the CCD. Use of these newly identified promoters, combined with the greatly increased sensitivity of bioluminescence detection by the CCD, thus provided a new dimension for the study of natural ecological populations during the bacterial colonization of plants.