摘要:

SummaryThe N‐substituted phthalimide, AC 94377, promoted the germination of dry‐stored seeds of 17 out of 24 weed species in Petri‐dish tests maintained at 22°C. In a further test it was able to substitute for light and/or alternating temperatures in promoting the germination of some species. AC 94377 was more active than GA, in stimulating Solanum nigrum seed to germinate. When mixed with soil in the laboratory, AC 94377 again promoted germination of S. nigrum but the level and persistence of activity differed between soils. In the glasshouse, with soil containing a natural weed seed population, more seedlings emerged from treated than from untreated soil but this number represented fewer than half of the apparently viable seeds present. Field applications of AC 94377 promoted the germination of hand‐sown seeds of certain weed species but did not increase the number of seedlings emerging from the natural weed s

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06591.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryWinter barley cv. Igri was grown in pots, either outside under cover, in a glasshouse or under controlled conditions and treated post‐emergence with isoproturon. There was a linear relationship between the subsequent weight of plants treated with 2.5 kg a.i./ha and either evaporation from a water surface between 2–7 days post spraying or cumulative temperature between sowing and spraying. The relationship between subsequent weight of plants treated to the foliage only with 5 kg a.i./ha and cumulative temperature between sowing and spraying varied between years 1984–86. The post spraying environment had the major influence on subsequent activity of isoproturon at 2.5 kg a.i./ha applied overall to barley under controlled conditions. There was a greater reduction in CO2exchange in plants grown after treatment under high compared to low relative humidity. When isoproturon at 5 kg a.i./ha was applied to barley plants with wet foliage, plants were slower to recover their initial rate of photosynthesis when kept wet for 24 h as compared with 11 h or when allowed to dry after treatment. Photosynthesis was decreased to a lesser extent under the same post spray conditions by 2.5 than by 5 kg a.i./ha and reduction was greater and recovery of photosynthesis slower in plants grown inside compared to ou

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06592.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryFive different navel sweet orange cvs or cv. selections, planted in the Citrusdal area of the western Cape Province, South Africa, were evaluated for their susceptibility to false codling moth infestation. The proportion of yield lost by two of them, cv. Bahianinha and the ‘Buffelspoort’ cv. selection, was lower than losses from the others evaluated. Damage due to other factors causing fruit abscission was also lowest in the cv. Bahianinha. The greatest number of eggs laid throughout the season was on the ‘Addo’ cv. selection, and losses due to the false codling moth were also greatest on this orange type. Rate of oviposition was significantly (P>0.05) lower on the cv. Bahianinha than on all the other types. Parasitism by a trichogrammatid egg parasitoid appeared to have no impact on overall egg mortality and did not account for any of the observed differences in fruit loss. The relationship between egg deposition and fruit loss was not clear and many factors require further investigation. Nevertheless, the distinct difference in rate of oviposition on the ‘Addo’ cv. selection, on the one hand, and on the cv. Bahianinha, on the other, indicates some consistent response to positive or negat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06593.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryAlthough Solanum brevidens could be infected with potato virus X (PVX), potato virus Y0(PVY0) and PVYN, no symptoms of infection were apparent and tests by double antibody sandwich ELISA, electron microscopy and sap transmission to local lesion test plants indicated that the titres of PVX were less than a tenth of those of PVY0and PVYNwere less than a hundredth of those in infected plants of PDH40, a susceptible dihaploid clone of S. tuberosum cv. Pentland Crown. Furthermore, PVY0‐ and PVYN‐ infected leaves of S. brevidens were a poor source of inoculum in aphid transmission tests. The possibility of a common mechanism and genetic basis of resistance to PVY, PVX and potato leaf roll virus in S. brevidens is discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06594.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryIn 1978 genetical variation for thiocyanate ion (SCN‐) was found in a kale population being selected for improved digestible organic‐matter yield. Four generations of half‐sib family selection for high and low SCN‐content in young leaves resulted in subpopulations with almost a twofold difference in their means, no overlap in their distributions, no observable reduction in their genetical variation, and only small differences in other traits. The total observed divergence in SCN‐content was 82% of that expected for a random mating population in linkage equilibrium in the absence of genotype x environment interactions. Average heritability on a single plot basis was low, namely 30%, but was increased to 46% with two replicates. This maximised the predicted response to selection for a fixed number of families selected and a fixed total number of plots.Bulks of the high and low subpopulations were assessed in a trial in 1988. Averaged over September and December harvests of young and mature leaves, SCN‐ contents were 104.5 and 58.5 mg/100 g DM, respectively. Of eight controls, cv. Merlin had the lowest content, 63.5, and cv. Proteor had the highest content, 89.6. Cultivar x harvest date, cultivar x leaf age and cultivar x harvest date X leaf age interactions were removed by a logarithmic transformation of the data. Stem contents were very low and variable with an overall mean of 10.9 in September and>5 in December, and no significant differences between cultivars or populations.The subpopulations will be valuable for research into possible effects of SCN content on the disease and pest resistance of kale and on the performance of anima

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06595.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryObservations had linked the disappearance of earthworms from a grass field to the presence of Artioposthia triangulata. An experiment demonstrated that this land planarian could severely and quickly reduce numbers of four earthworm species. Two different approaches to sampling A. triangulata were investigated on a grassland site. The first used four different trap types (wood, ceramic tile, ‘corriboard’ plastic and 5 mm polystyrene beneath a ceramic tile) measuring 15 cm x 15 cm which were compared over a period of 18 wk. The second used one, or two, applications of dilute formalin solution to quadrats followed by counting the residual planarians by hand‐sorting the soil beneath the quadrat to a depth of 30 cm. The polystyrene traps were the most effective for detecting the presence of A. triangulata. No planarians were ever found by hand‐sorting after two formalin applications and it was concluded that formalin sampling provided a good estimate of the population density. Counts under traps were not related to absolute estimates of population densities so polystyrene type traps should only be used for detection of the planarians. A multiple regression relationship of A. triangulata weight over time in 5% formalin is presented and allows the original liveweight to be calculated from the weight in preservative. Planarian and earthworm population densities in eight fields were sampled and the planarians were found to be randomly distributed. Counts of planarians in 0.25 m2quadrats were not related to numbers of earthworms but overall field population densities were. It is concluded that A. triangulata is a severe threat to the earthworm populations of Northern

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06596.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryAn investigation was undertaken to examine responses of mangoes cv. Kensington Pride to irradiation treatment.Gamma irradiation of preclimacteric fruit increased fruit respiration immediately after treatment, delayed the time to attain the climacteric respiratory peak and reduced the magnitude of this peak rate. Fruit softening was unaffected whereas skin colour development was strongly inhibited by irradiation treatment. Inhibition of skin degreening was half‐maximal at a dose of 200 Gy. Exposure to ethylene failed to reverse this inhibition. Less mature fruit were more strongly affected by irradiation treatment. Fruit which were partially ripe and in their climacteric rise at time of treatment were largely unaffected by irradiation. These results are discussed in terms of the utility of irradiation technology for commercial disinfestatio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb06597.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY