摘要:

SUMMARYWhen sixth abdominal ganglia of the cockroachPeriplaneta americanawere irrigated continuously with diazinon solutionin situ, its effects on nerve conduction and cholinesterase activity closely resembled those of diazoxon; spontaneous activity and after‐discharge increased until conduction was blocked, which happened while some cholinesterase was still uninhibited. The symptoms were only slightly relieved by irrigating ganglia with saline.Though the LD50's of diazinon and diazoxon applied topically to adult maleP. americanawere similar (2.5 ± 0.33 and 4.5 ± 0.38 μig. per insect), diazoxon was about 300 times more active than diazinon against nerve function and cholinesterase activity in the sixth abdominal ganglion. This is probably because in the nerve preparations contact between the insecticide and the tissues surrounding the nerve cord, which in whole insects convert diazinon, a thionophosphate, into its phosphate analogue diazoxon, a more active anticholinesterase, was minimized. Indeed, taking into account the evidence of workers who previously comparedin vitrothe anticholinesterase activities of several thionophosphates with those of their phosphate analogues and found the phosphates much more active, the effect of diazinon on cholinesterase activity and nerve function in our experiments was unexpectedly great. By applying diazinon to nerve cords with SKF 525‐A, a compound likely to prevent oxidation of diazinon to diazoxon, an attempt was therefore made to decide whether diazinon directly affected nerve conduction or whether the effect resulted either from its conversion to diazoxon within the nerve tissue or from impurities in the diazinon used. Results were inconclusive, for SKF 525‐A (p‐diethylaminoethyl diphenylpropylacetate hydrochloride) not only failed to prevent the inhibition of cholinesterase, but interfered with the action of both diazinon and diazoxon on nerve conduction, and itself affected nerve conduction when applied alone. The possibility that diazinon is itself a mild anticholinesterase was not excluded.SKF 525‐A applied to sixth abdominal ganglia at 2 × 10‐4M blocked conduction from cereal nerves to giant fibres in 50–97 min. and at 4 × 10‐5M decreased the post‐synaptic response; applied to giant fibres at 2 × 10‐4M it blocked conduction in 90–208 min. The effects of the larger concentration were not completely reversible. Although SKF 525‐A has been widely used to study the metabolism of drugs, its direct effects on conduction in nerve axons seem not

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04411.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYThe antibiotic terramycin at 0.2% concentration was consistently effective in greatly reducing the populations ofAphis fabaeonVicia fabawhen sprayed on larvae on and off the plant. The insects were not killed, but their fertility was decreased by over 97% in the first generation, leading to total sterility in the second generation. At 0.01% concentration, terramycin was not effective and only moderately so at 0.1%Larval development was invariably delayed by 1 day and the weight and size of the resulting adults were significantly reduced. After the most effective treatments, the adults were very inactive in their feeding and excretion, and sometimes became completely sterile. Even when the aphids reproduced, they ceased to do so after 6–10 days in different terramycin treatments and frequently the larvae were born dead. The affected insects could not, apparently, regain their reproductive capacity even after their transfer to untreated plants.When the insects were sprayed on the plants, terramycin in water was as effective as with surfactants: but when the insects were sprayed off the plants an oxyethyl phenol derivative (NP 10) greatly increased the efficiency of terramycin: surfactants alone had no effect on the insects.The other four antibiotics, namely tetracycline, aureomycin, chloramphenicol and reverin were not effective at the 0.2% concentration when the plants alone were sprayed before introducing the apids. The addition of glycerin to the antibiotics and keeping plants in a high humidity for 24 hr. after the treatment also had no effec

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04412.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYRed clover plants, collected from nine widely separated permanent pastures in England and Wales, were tested for sap‐transmissible viruses. Viruses were identified by the symptoms they caused in test plants, by electron microscopy, and by serological tests. Of the 265 plants tested 14% were infected. Only pea mosaic virus was common and widespread; it was found in 8% of the plants, and in seven of the fields. Other viruses isolated were arabis mosaic, bean yellow mosaic, red clover mottle, and red clover vein mosaic; only red clover mottle virus produced diagnostic symptoms in red clover. No viruses were detected in seedlings grown from seed from eighty‐nine commercial seed crops. Attempts to transmit red clover mottle virus by the CollembolanSminthurus viridisL., which is common on red clover, fai

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04413.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYCocksfoot mottle virus (CFMV) was transmitted by manual inoculation of sap to cocksfoot (Dactylis glomerataL.), wheat, oats and barley, but not to nineteen other monocotyledonous and thirteen dicotyledonous plant species. The virus was also transmitted by cereal leaf beetles (Lema melanopaL.). Adult beetles infected plants more frequently than larvae, and remained infective for up to 2 weeks after they had fed on infected plants. Seed from infected cocksfoot and oat plants produced virus‐free seedlings.The infectivity of sap was lost during 10 min. at 65° C., and 2 weeks at 20° C., but survived many months at — 15° C.Purified virus preparations, made by various methods, contained numerous nearly spherical particles, about 30 mμ in diameter. In electron micrographs some of the particles were penetrated by negative stain though most appeared intact. However, all the particles migrated together in a centrifugal (sedimentation coefficient = 118 S) or electrophoretic field. The ultraviolet absorption spectrum, and the phosphorus and nitrogen contents of the virus preparations, were typical of a nucleoprotein containing about 25 % nucleic acid.Serological tests failed to show any relationship between CFMV and eleven other viruses with particles of similar shape a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04414.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYVirus‐free individuals of the plant‐hopperJavesella pellucida(Fabr.) infected plants with European wheat striate mosaic virus (EWSMV) after being injected at 5° C. with extracts of either plants or hoppers, but extracts of hoppers provided a better inoculum. Hoppers were unable to infect plants until at least 8 days at 20–25° C. after they were injected, and nymphs fed on infected plants similarly required 8 days before they gave infective extracts. Few hoppers survived more than a week after injection with untreated extracts of hoppers or with material sedimented from them by centrifuging the extracts at 8000g, but 60–70% survived injection with purer virus preparations. Injection of the virus seemed harmless, because as many hoppers survived CO2anaesthesis + injection, whether or not they later infected plants, as survived anaesthesis without injection. Attempts to determine the properties of the virusin vitrogave inconsistent results, but virus from hoppers was still infective after 10 min. at 30° C, 36 hr. at 5° C, precipitation at pH 4.0, storage for several months at ‐15° C, or at a dilution equivalent to 0.0014 g. hopper/ml. The best extraction medium contained 0.2 M‐Na2HPO4+ ascorbic acid + 0.01 M‐DIECA at pH 7.0–7.3. In sucrose density‐gradients, EWSMV sedimented more slowly than tobacco mosaic virus. No specific particle with which infectivity could be correlated was seen

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04415.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYTransmission through seed of crop and weed plants seems to be characteristic of nematode‐borne viruses. It occurred with tomato black ring virus (TBRV) in nineteen species (thirteen botanical families), with arabis mosaic virus (AMV) in thirteen species (eleven families), with raspberry ringspot virus (RRV) in six species (five families), and also, in more limited tests, with tomato ringspot, cherry leaf roll and tobacco rattle viruses. A remarkable feature was that infected seedlings, except those containing tobacco rattle virus, often appeared healthy. The occurrence and extent of seed‐transmission depended on both the virus and the host plant. In many progenies more than 10%, and in some 100%, of seedlings were infected. The viruses were transmitted through at least two or three generations of seed of those host species tested. After 6 years' storage, TBRV‐ and RRV‐containing seed ofCapsella bursa‐pastorisandStellaria mediagerminated to give infected seedlings.In controlled crossing experiments with strawberry and raspberry, virus was transmitted to seed from both male and female parents but, at least in raspberry, the presence of competing virus‐free pollen much decreased the ability of pollen from infected plants to set seed. There was no evidence that healthy mother plants became infected when their flowers were pollinated with infe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04416.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYVirus‐free populations of vector nematodes can acquire tomato black ring (TBRV), raspberry ringspot (RRV) and arabis mosaic (AMV) viruses from weed seedlings grown from virus‐carrying seed. When soils from fields where nematode‐borne viruses occurred naturally were air‐dried to kill vector nematodes and then moistened, TBRV and RRV occurred commonly in the weed seedlings that grew, but AMV occurred only rarely. Similar tests did not detect tobacco ringspot, grapevine fanleaf or tobacco rattle viruses in weed seeds in the single soil studied in each instance, although these three viruses are also seed‐borne in some of their hosts. Many weed species, when infected experimentally, readily transmit TBRV and RRV to their seed, but the viruses were much commoner in naturally occurring seed of some of these species than of others. These discrepancies between the frequency of seed‐transmission of viruses from experimentally infected plants and the extent of natural occurrence of infected seed seem largely to reflect the host preferences of the vectors.InfectiveLongidorus elongatuskept in fallow soil retained TBRV and RRV only up to 9 weeks. When weed seeds in the soil were then allowed to germinate, the nematodes reacquired virus from the infected seedlings. Some weed species were better than others as sources of virus. Persistence of these viruses in fields through periods of fallow or fasting of the vector therefore depends on a continuing supply of infected seedlings produced by virus‐containing weed seeds. This is probably less true of viruses like AMV and grapevine fanleaf, which persist for 8 months or more in their vectors (Xiphinemaspp.). A few seeds containing TBRV and RRV were found in soils free of vector nematodes, suggesting that the viruses are disseminated in weed seed. This probably explains how TBRV and RRV have reached a large proportion ofL. elongatuspopulations in eas

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04417.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYPure cultures of six races ofDitylenchus dipsaciderived from a single female, namely, lucerne race (LR), red clover race (RCR), white clover race (WCR), narcissus race (NR), tulip race (TR) and oat race (OR) were inoculated into eight plant species growing in pots. Onion was host to all six races, and tulip to all except RCR, whereas lucerne was susceptible only to LR and slightly to WCR. Hyacinth was not very susceptible to any race. The TR and OR were the most polyphagous. Severe symptoms were not necessarily associated with large nematode populations. Parthenogenesis did not occur. Ten fertile hybrids between races were produced and the host range of five of these was tested. On average the hybrids multiplied less than their parent races and their host ranges showed no relationship to those of their parent races. RCR and TR inoculated together into tulip produced significantly fewer nematodes than did TR alone and more than RCR alone. Mixed populations of races occur in nature which are probably a mixture of parental races, their hybrids and back‐crosses. Repeated back‐crossing of the hybrids with parental types and the slower multiplication of the hybrids is an explanation for the variation in host range of known races and the failure to record new ra

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04418.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYMinimum and maximum net assimilation rates were determined from calculated curves of closest fit to data for 2 years. The minimum (14 g./m.2/week) occurred in mid‐December, immediately before the shortest day, and the maximum (78 g./m.2/week) between 27 June and 8 July, just after the longest day. The northern limit at which the tomato cannot maintain vegetative growth under glass in mid‐winter is probably latitude 59–60° and is determined by a limiting daylength of approximately 6 hr. The proportional reduction in net assimilation rate by shading was independent of the time of the year. The photosynthetic system of glasshouse tomato plants is not light‐saturated in midsummer in southern

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04419.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

SUMMARYExperiments on leaves of tomato, sugar beet and cocksfoot show that uptake of diquat and paraquat, although rapid in the light, is increased by darkness and therefore takes place through the cuticle and not through stomata. Darkness for as little as 4 hr. increased uptake almost twofold.Diquat and paraquat are rapidly and strongly adsorbed both to leaf tissue and to extraneous matter on the leaf surface.Uptake in the field is so rapid that rain immediately after treatment has little adverse effect.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1967.tb04420.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY