摘要:

SummaryA method is described for obtaining from plants partially purified preparations of mycoplasma‐like organisms (MLO) which are suitable for use as immunogens for polyclonal or monoclonal antibody production, and as antigens for directly coating ELISA plates. Using this method a mouse monoclonal antibody to primula yellows MLO was prepared, and its characteristics compared with those of primula yellows polyclonal antibodies from rabbits and also against polyclonal antibodies made to similar preparations of European aster yellows MLO. No serological distinction was obtained between any of the homologous or heterologous combinations of antibody and MLO preparation using ELISA, fluorescence microscopy with FITC‐labelled antibodies, or immunoprobes of western blots of partially purified MLO preparations. By contrast, there were no cross‐reactions between the primula or aster yellows antibodies or MLO preparations and preparations of clover phyllody or tomato big bud MLOs or their respective polyclonal antibodies. The primula yellows MLO monoclonal and polyclonal antibodies, and also the European aster yellows MLO polyclonal antibodies, all appeared to recognize only a single major antigen of approximate M, = 22 400 daltons. Some possible explanations for the apparent specificity of the polyclinic antisera for a single antigen, and the relevance to MLO preparation procedures are disc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06791.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryUsing a single soil, a comparison was made of six well‐known techniques for the isolation of nematophagous fungi. Each technique was tested for its ability to isolate the fungi present with regard to the number of species recovered, the number of plates needed to be 95% sure of isolating all the species possible and the amount of soil required. The advantages and disadvantages of each method are discussed. The results show that specific techniques are required for the isolation of endoparasites and predators respectively. The soil sprinkling technique and the Baermann funnel technique are shown to be the most efficient methods overall, with six and seven replicates required for 95% probability of isolating all the predator and endoparasite species respectivel

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06792.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryIn an experiment prepared in autumn, weed numbers were not affected by covering the soil with clear perforated polyethylene. Weed growth was enhanced, however, and the fresh weight at the time of polyethylene removal in spring was more than three times greater on the covered compared with the uncovered areas. In a similar experiment prepared in spring, covering with perforated polyethylene increased weed numbers by a factor of two and weed fresh weight by a factor of seven. The performance of a number of herbicides used in carrots, in terms of percentage reduction in weed number and weed fresh weight, was similar under covers and in the open. The most effective weed control was achieved with broad‐spectrum herbicide treatments, particularly under the polyethylene, since surviving weed seedlings grew rapidly in the protected environment. When weed control was good, covering enhanced carrot yield. Measurement of the distribution of herbicide residues in the soil demonstrated that persistence was increased and movement in the soil decreased by covering with polyethylen

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06793.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe mechanism by which reduced‐height genes, Rht1and Rht2influence yield and harvest index (HI) were investigated in dwarf (D, Rht1Rht2), semidwarf (SD‐1 and SD‐2, Rht1rht2and rht1Rht2, respectively), and tall (T, rht1rht2) near‐isogenic lines (isolines) derived from winter wheat cv. Burt. Dry matter accumulation, yield, and assimilation, distribution, and retention of14C label from photosynthetic assimilation of14CO2, was followed in field‐grown plants in Connecticut, USA. The relationships among the isolines were similar over the two years of study. The tall isoline ranked highest in grain yield and biomass, but had a small HI; SD‐1 was similar to T in yield and biomass, but had the largest HI; SD‐2 was similar to SD‐1 in HI, but its yield and biomass were less than SD‐1 and T; and D yielded the least grain and biomass and had a small HI similar to T.Following photosynthetic assimilation of14CO2during grain filling, the distribution of14C in ears at maturity was similar for SD‐1, SD‐2, and T. When labelled shortly after anthesis or late in grain filling, the distribution of14C to the mature ear of D was less than that for other isolines. At maturity D also retained the smallest amount of the radioactivity initially assimilated. The low yield and HI of D may be related to its inability to retain photosynthate and distribute it to the grain. The SD‐1, SD‐2, and T isolines did not differ in retention at maturity of14C in the whole plant. When labelled shortly after anthesis, stems of T retained more14C, which may represent a tendency to sequester more photosynthate in its stems that would reduce its HI at maturity. In contrast, the yield of SD‐2 was limited

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06794.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe response of apples cv. Cox's Orange Pippin to storage in flowing streams of air and nitrogen mixed to generate atmospheres ranging from 0.5% to 2% oxygen was examined in two seasons. The benefits of reducing store oxygen concentrations below 1.25% were small but storage in 0.75% may be advantageous for Cox's Orange Pippin apples in seasons when flesh firmness is low at harvest. Ethanol‐induced flesh breakdown was recorded in samples stored in 0.5% O2in one season and the risk of low temperature breakdown was increased in oxygen levels below 1.25%. Ethylene production was reduced by lowering the oxygen concentratio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06795.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryHokkanen&Pimentel (1984) proposed a novel approach for the selection of biocontrol agents. They advocated the selection of agents from a relative of the weed plant rather than from the target weed species itself. The new relationship that such agents would have with the weed would be characterised by a relative lack of homeostasis compared with the old herbivore‐plant associations traditionally used in weed biocontrol, and would consequently be more effective. There are few examples to support these contentions because of the traditional use of old herbivore‐plant associations in weed biocontrol.In the present study, herbivore‐plant associations in agricultural situations, which are analogous to agent‐weed associations, are examined to assess the potential of new associations for weed biocontrol. The herbivores on 14 introduced crop plants which have salient similarities to the major weeds in the south‐western Cape were surveyed: (a) 68% of the 188 insect and mite herbivores are indigenous species in new associations with these host plants, and (b) of the five most damaging pests on each of 13 of the crop plants, 53% are in new associations with the plants. Of the 40 most important agricultural pests in South Africa, 58% are in new associations, confirming these results. About 50% of the insect and mite herbivores in new associations with their host plants are oligophagous, indicating that new associations are not necessarily characterised by polyphagy and hence unsafe for use in weed biocontrol.We conclude that new associations between herbivore species and host plants have strong potential in weed biocontrol because (a) their frequency in agriculture indicates that they can easily be established in weed biocontrol situations, (b) they are as damaging as old associations and (c) they are not necessarily unsafe as regards host specificity. We therefore advocate the use of both the classical approach and that of Hokkanen&Pimentel (1984). Our support for Hokkanen&Pimentel (1984) is, however, based on evidence and rationale clearly different to theirs, and we provide novel guidelines, which can be routinely and practically applied in the selection of agents for weed b

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06796.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe lipid profile ofPleurotus sajor cajuwas studied in relation to mycelial and sporophore growth and different cultural factors. The growth was characterised by lipid synthesis during mycelial growth and utilisation during sporophore growth. The degree of instauration increased during mycelial growth and decreased during sporophore formation. The fatty acid composition of mycelium and sporophore was similar, linoleic acid (C18:2) being the most dominant acid in both. C:N ratio had a significant (P<0.05) positive effect on mycelial dry weight; however, per cent total lipids was similar. Non‐polar lipids became more unsaturated as the temperature was raised from 10° to 25°C and pH from 3.0 to 6.0, but declined when the cultures were aerated. Mycelial dry weight increased significantly (P<0.05) when the liquid medium was supplemented with lipids. In general, fatty acids with carbon chain length C16and C18stimulated the growth of mycelium. Supplementation of solid substrate (cotton seed hulls) with safflower oil, soybean oil or rice bran significantly (P<0.05) increased the yield of sporophores. Total lipids and ratio of non‐polar to polar lipids were not affected by lipid supplement

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06797.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryCarrot seeds cvs Chantenay and Amsterdam were harvested on several occasions from crops grown in 1985 and 1986, from the time they had reached or were close to their maximum dry weight and were starting to turn brown.Maximum seed dry weight occurred approximately 40–45 days after flowering (DAF) in both cultivars. Maximum germination (International Seed Testing Association 14‐day count) occurred 40 and 55 DAF in cvs Chantenay and Amsterdam, respectively, but the maximum 7‐day count and the minimum coefficient of variation of embryo length did not occur until 60 DAF in cv. Chantenay and 55 to 65 DAF in cv. Amsterdam. Percentage germination was negatively and linearly related to seed moisture content, chlorophyll a + b content in the seed coat and seed distortion, measured on a modified tensile‐testing machine, the relationships accounting for 77, 71 and 64% of the variance in the 7‐day germination count, respectively. The corresponding values for the 14‐day count were 63, 61 and 50%. A simple field test for monitoring seed maturity

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06798.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe phosphorus content of a field‐grown strawberry crop was monitored over one growing season and the allocation of P to different plant parts determined. In the early part of the season, leaves were the major sink for P and this was partly supplied by redistribution from rhizomes. Once flowers were initiated, these became the major sink and their P requirement was satisfied by new uptake. The calculated rates of P inflow to the roots in this phase of growth were so large that it was necessary to postulate not only that P uptake was assisted by mycorrhizas, but that the whole root system, including the old, brown roots, was active. The implications of this conclusion for concepts of vesicular‐arbuscular mycorrhizal function under field conditions are discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06799.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe effects of different applied nitrate concentrations (1 to 50 mol m3) on growth ofPhaseolus vulgariscv. Seafarer at temperatures around 15°C was examined. Total plant dry weight and carbon content decreased sharply with increased applied nitrate 1 to 10 mol m‐3then decreased slightly with further increases in applied N. Total plant reduced ‐N content increased sharply with increased applied nitrate concentration from 1 to 5 mol m‐3, changed little with increased applied nitrate from 5 to 25 mol m‐3, then increased when applied nitrate was increased from 25 to 50 mol m‐3. Nitrate concentration in all tissues increased sharply with applied nitrate increased from 1 to 10 mol m3and showed a further increase at 50 mol m3applied nitrate.Fresh weight to dry weight ratio for all leaves and specific leaf area for all secondary leaves increased sharply with applied nitrate concentration from 1 to 5 mol m‐3then decreased with applied nitrate 25 to 50 mol m3Secondary leaf chlorophyll concentration decreased sharply when applied nitrate increased from 1 to 5 mol m‐3but increased with applied nitrate from 25 to 50 mol m‐3. Initially, the rate of leaf extension was greater at 20 mol m‐3applied nitrate than 1 mol m‐3applied nitrate.It is proposed that decreased growth with increased applied nitrate in the range 1 to 10 mol m‐3is due to increased leaf damage caused by a greater

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06800.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY