Detection of aphid remains in predatory insects and spiders by ELISA

An ELISA was developed which would detect and quantify ingested aphids in predators found in and around cereal crops. The detection limit of the assay was less than one hundredth of an homogenised adult aphid. Tests with 13 species of aphid showed that those which had been used as the principal immunogens reacted most strongly in the assay. Nearly a hundred species of invertebrates, both predators and alternative prey, have been tested in the assay and no evidence of significant cross-reaction was found with any of these species or with a number of samples of plant material on which aphids may be found. Aphid material could still be detected in predators which had been stored for up to 7 days in 4% formalin or 70% ethanol.     

Virus-Infected Pollen Grains in Paeonia emodi

Tubular virus particles, 25 x 190 nm in length, reacting stronglyin gel diffusion tests and immunoelectron microscopy to tobaccorattle virus antiserum, were detected in pollen grains of aplant of Paeonia emodi. Relative to leaf cells, the pollen grainscontain virus in high concentration, particles being arrangedside by side in long crystalline arrays distributed randomlythroughout the cytoplasm. Presence of the virus is correlatedwith anomalous pollen development and degeneration of mitochondriaand other organelles. The observations are discussed in relationto male sterility and pollen dimorphism in this plant and itsfailure to respond in anther/pollen culture. Key words: Peony, Pollen, Viral Infection     

A large improved rotary trap for sampling aerial invertebrates

A large rotary trap designed to measure aerial spider density is described. A comparison of the rotary trap catch and a suction trap catch of spiders and other invertebrate groups showed that the rotary trap was operating at a greater efficiency for most groups. For spiders and non-staphylinid beetles the two traps caught equal numbers. There were no differences in the species composition of spiders between the rotary and suction trap catch.     

Photocontrol of Growth, and of Anthocyanin and Chlorogenic Acid Production in Cultured Callus Tissues of Haplopappus gracilis

Cultures of dark-grown Haplopappus callus (strain AI) were exposedto continuous blue, green, red, far-red, and white light for33 days at energy levels of approximately 10 J m^-2s^-1. Growthwas suppressed in all but far-red. Blue had the greatest suppressiveeffect, green the least; red and white were about equally effective.Mean cell generation times were increased from 8–8 days(dark control) to 12.5 days in red light and 20.5 days in blue.There was a slight increase in mean wet weight per cell in bluelight but a slight decrease in red, whereas there was almosta twofold increase in mean dry weight per cell in blue and littlechange in red. In contrast, far-red stimulated growth; the meancell generation time was reduced to 6–5 days and therewas little change in wet or dry weight per cell. Anthocyanin synthesis was promoted by all wavebands except far-red.Blue had the greatest effect, then white, red, and green inthat order. In blue light the pigments accumulated rapidly,but only during the early stages of culture. The maximum amountper cell was attained after 7 days and thereafter the valuesdeclined. In red, however, the pigments accumulated relativelyslowly, and the maximum cell content was not attained until22 days; the amount attained was less than half that attainedin blue light. Initially, the ratio of cyanidine-3-glucosideto cyanidine-3-rutinoside exceeded 5.0 in blue light, but theratio fell to almost unity with time. This probably reflecteda rapid initial synthesis of the glucoside accompanied by asteady conversion to the rutinoside. Blue light was also more effective than red in acceleratingchlorogenic acid production. The response to blue light occurredafter the initial rise in anthocyanins and continued for therest of the culture period. The data are discussed in relation to similar high-energy photoresponsesreported for intact systems.     

Pollen Ultrastructure in Anther Cultures of Nicotiana tabacum: I. EARLY STAGES OP CULTURE

Ultrathin sections of 2- and of 5-day-old cultured tobacco anthersinoculated at the stage of the first pollen mitosis were examinedin the electron microscope in an attempt to identify early structuralchanges associated with pollen embryogenesis. On both samplingoccasions grains were observed with structural features of typicalbicellular gametophytes but lacking starch. Some of these grainswere atypical in that they possessed numerous small vacuolesin both cells. There was no obvious change in organelle structurein either cell from 2 to 5 d, though there was evidence of anincrease in ribosomes and other organelles in the vegetativecell. Gametophytes possessing starch were also present but inrelatively low numbers. At 5 d, pollen tubes and grains havingstructure characteristic of germinating pollen were also encountered. It is concluded that embryogenesis begins after a short periodof normal gametophytic differentiation which, during the first2 d of culture, proceeds at much the same rate as in vivo. Subsequentlythe rate declines and gametophytic processes gradually cometo a halt. Starch formation is suppressed.     

Temperature and prey capture: opposite relationships in two predator taxa

Abstract 1. All other things equal, predator capture rates are expected to depend on encounter rate with prey, prey escape capability (including prey defences), and on predator agility. Ectotherm predators and their prey both respond to increasing temperature by increased activity, i.e. predators increase their search area and prey may enhance their escape capability. This means that, as temperature changes, the ability of a predator to catch prey will decrease, increase, or remain unchanged depending on the relative effect of temperature on predator and prey. Their responses may further be differentially moulded by light conditions depending on whether the predator is diurnally or nocturnally active. It was hypothesised that flying Diptera are vulnerable to carabid beetles only at low temperatures and over the full temperature range for spiders because carabids, in contrast to spiders, are not built to catch swiftly moving prey. 2. The first experiment examined the spontaneous locomotor activity of the predators and of fruit flies at different temperatures (5, 10, 15, 20, 25, and 30 °C) and light conditions (light, dark). A second experiment examined the effect of temperature and light on the predation rate of two carabid beetles (Pterostichus versicolor and Calathus fuscipes) and two spiders (Clubiona phragmitis and Pardosa prativaga) using fruit flies (Drosophila melanogaster) as prey. 3. All four predators and the fruit fly increased their locomotory activity at higher temperatures. Activity of the carabid beetles peaked at intermediate temperatures; spiders and fruit flies were most active at the highest temperatures. Predation rate of the spiders increased with temperature whereas the beetles caught flies only at low temperatures (5 and 10 °C). 4. Diurnal variation in temperature may bring different prey groups within the set of potential prey at different times of the day or at different seasons. The ability of many carabid beetles to forage at low temperatures may have nutritional benefits and increases the diversity of interactions in terrestrial food webs.     

Digestion rate in relation to alternative feeding in three species of polyphagous predators

Abstract. 1. Disappearance of different amounts of aphid ingested by three species of polyphagous predators, the carabids Bembidion lampros (Herbst) and Nebria brevicollis (F.) and the staphylinid Philonthus cognatus Stephens, was monitored by a quantitative enzyme-linked immunosorbent assay (ELISA). The effect on the rate of inactivation of prey antigens by the ingestion of subsequent, non-aphid food was also studied.
2. Antigen inactivation was significantly more rapid in the staphyilinid than in the carabids.
3. No statistically significant differences were found in the rate of antigen inactivation between beetles which consumed only aphids and those which were given a different type of food after feeding on aphids; the detection period was longer in the former groups. A higher proportion of beetles with low levels of aphid antigen were found earlier in the latter group.
4. The results did not unequivocally support the prediction derived from optimal digestion theory that beetles without continuous access to food would retain an initial meal longer than beetles with unlimited access.     

Pollen-Derived Haploids of Nicotiana Knightiana, N. raimondii, and N. attenuata

Haploid plantlets were obtained in large numbers in three diploid,24-chromosome species of Nicotiana by culture of anthers ator just past the first pollen mitosis. The three species wereN. Knightiana, N. raimondii, and N. attentiata. Efficiency ofhaploid production varied from about 10 per cent in N. attenuatacultures to 30 and 38 per cent respectively in cultures of N.raimondii and N. Knightiana. H-medium without hormones and standardcultural conditions were used. N. Knightiana appeared to beespecially suitable for haploid studies on account of its highplantlet productivity, low chromosome number, and distinctivekaryotype.     

Observations on the number of cereal aphids on the soil in relation to aphid density in winter wheat

The numbers of cereal aphids on the soil surface was assessed by soil samples and by counting the numbers captured in pitfall traps. A relationship was found by both methods between the density of aphids on the plants and the numbers of aphids on the soil. This relationship indicated that a higher proportion of the aphid population was on the soil surface at the lower densities on the plant. Reasons for this relationship are suggested and discussed.