摘要:

SUMMARYDuring the period November to March a threefold increase in CO2concentration had only a small effect on the growth rate of tomato seedlings, variety Eurocross B. Although net assimilation rates were increased, some inhibitory effects of increased CO2concentration on leaf growth were found when the seedlings were very small. The increase in dry weight was equivalent to that made in a few days by plants grown with naturally occurring amounts of CO2. There was no increase in the rate of flower initiation. Using supplementary illumination for 17 hr. per day with high‐pressure mercury vapour lamps made it possible to produce in November‐December seedlings similar to those grown during March‐April with natural illumin

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03828.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYWhen14CO2was supplied to three varieties of wheat in the field translocation of carbohydrates took place freely throughout young plants, but after the stems elongated the tillers became autotrophic.The efficiency with which carbohydrate was translocated to the grain increased during the first 4 weeks after anthesis and then fell. Translocation from the glumes and flag leaves was almost entirely towards the grain; that from the second and third leaves was partly towards the grain and partly downward, with evidence of varietal differences in behaviour.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03829.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYField experiments in 1961 and 1962 with four winter wheat varieties (Professeur Marchal, Cappelle‐Desprez, Hybrid 46 and Holdfast) compared three water regimes: irrigation to prevent the soil water deficit exceeding 2 in.; shielding from rain; and normal rainfall. The experiments were done on soils selected for their liability to drought. Grain yield was decreased by water deficit; the effects differed between varieties, but the varietal differences were not consistent in the 2 years.In glasshouse experiments, plants of Cappell‐Desprez were subjected to drought for 3–4 days during ear development and subsequently watered normally. When this treatment preceded pollen meiosis by a few days many of the lower florets of each spikelet were male‐sterile but female‐fertile. Also there was often proliferation, within the spikelet, of normally fertile florets above the male‐sterile ones, showing that the number of florets formed may increase until a late stage in ear development.The results of the field experiment suggested that grain yield was restricted by the capacity of the grains as sinks for photosynthates. If so, a genetic improvement in grain yield could be obtained by breeding for an increase in number of florets p

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03830.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYTulip bulbs produced in sand culture with three rates each of nitrogen, phosphorus and postassium in factorial combination were subsequently grown for one season with complete nutrients in order to study the residual effects of the previous treatments. The bulbs included the progeny of large (II cm). and small (7 cm.) Golden Harvest after one season of differential nutritional treatments and of large Golden Harvest (II cm). and Elmus (12 cm.) after tow such seasons.The early stages of growth, became less apparent by early March, but many of the bulbs previously deprived of nitrogen produced only single leaves and no flowers. The favourable effect of nitrogen on the weights of Golden Harvest bulbs was less marked at lifting than at planting time, but remained highly significant. The yield of Elmus bulbs showed particularly marked responses to both nitrogen and phosphorus. Other residual effects included decreased leaf area of bulbs previously deprived of nitrogen and phosphorus, and slightly earlier flowering with increasing levels of nitrogen.Growth in complete nutrient solution decreased the differences in amounts of major nutrients in the bulbs. The percentage of nitrogen in Golden Harvest bulbs, and of phosphorus and potassium in both varieties, nevertheless increased significantly with the levels of these nutrients in the previous seasons.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03831.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYSeedings of Amelonado Cocoa and of two progenies obtained by crossing Iquitos (Upper Amazon) parents were infected with three strains of cocoa swollen‐shoot virus (CSSV) and with cocoa mottle‐leaf virus (CMLV). CSSV strain I A had the most severe effects on the growth and canopy condition of all varieties. All four virus isolates had more effect on the growth of Amelonado than on the Iquitos progenies, except that CSSV strain I W affected the growth of Amelonado and one of the Iquitos progenies equally, as did CMLV which caused the greatest decrease in the first crop of all varieties. The relative virulence of different CSSV strains in any one variety can be assessed from single criteria such as length of latent period or effect on growth; CMLV had a shorter latent period than CSSV Strain I A but less effect on gro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03832.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYField experiments on the effect of residues of aldrin and dieldrin in the soil on the beetle predators of the cabbage root fly, showed that populations of adult carabid and staphylinid predators were altered by aldrin/dieldrin residues at concentrations of 0.06 p.p.m. and above. The lower insecticidal concentrations were aged residues which had become intimately mixed with the soil. Although the residues reduced the numbers of trappedAleocharaspp., concentrations below 0.5 p.p.m. increased the numbers ofBembidion lampros, probably because their movement was stimulated by the insecticide.Harpalusspp. andFeroniaspp. were unaffected by residues below the concentration toxic to cabbage root‐fly eggs and larvae. The reductions of the predators implied by the trapping records increased the survival of the cabbage root‐fly eggs and larvae, thus leading to augmented damage to cauliflowers, cabbage and Brussels sprouts, which resulted in reductions in yield of up to 70%.Larval and pupal parasitism byAleocharaspp. andIdiomorpha rapaewere also reduced by the insecticide residues, although concentrations of 0.2 p.p.m. and above were required to decrease parasitism byI. ra

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03833.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe number of Aphis fabae Scop. per plant and per acre developing on field beans (Vicia fabaL.) was inversely related to seeding rate (i.e. plant density) except sometimes at very low rates; with equal numbers of plants per acre, fewer aphids developed on plants in rows 11 in. than 22 in. apart.Plots sown in mid‐March with more than about 150,000 plants per acre were more attractive than less dense stands to colonizing alateA. fabae, but established colonies multiplied most on the sparsest and least on the densest plots.The number of plants per acre infected by pea leaf‐roll virus was inversely related to planting density. There were more virus‐infected plants on II in. than on 22 in. spaced rows‐in contrast to the numbers of A. fabae. A single spray with demeton‐methyl, timed to controlA. fabae, did not significantly decrease virus incidence.Grain yields of sprayed plots were little altered by increasing the seed rate above a critical minimum, except in one year when the densest crops lodged. Increased yields from spraying were closely related to the numbers ofA. fabaeon unsprayed plots. Dense planting (more than 400,000 plants per acre) prevented or greatly decreased losses caused byA. fabaein unsprayed plots except in one year when the aphids were exceptionally

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03834.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYLeaves of virus‐free sugar‐beet plants rarely became infected withAlternariaspp. in two field experiments at Cambridge in 1965. Infection with beet yellows virus (BYV) increased susceptibility of plants toAlternariaonly slightly but infection with beet mild yellowing virus (BMYV) increased it greatly. There was a close association between the severity ofAlternariasymptoms, shown by different breeding lines and varieties of sugar beet, and the losses of sugar yield which they sustained after infection with BYV and BMYV. Many lines and varieties were resistant toAlternariaeven when infected with BMYV and their resistance seemed to be inherited as a dominant character. Individual plants of any one line or variety differed greatly in resistance toAlternaria, suggesting that selection should improve the present level of resistance.Spraying the foliage ofAlternaria‐susceptible varieties with fungicides had little effect on the severity ofAlternariasymptoms or on sugar yield. This was probably because the wet summer of 1965 was ideal for the spread ofAlternariaand because rain washed the fungicide deposits from the sprayed l

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03835.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe natural spread of Erysiphe cichoracearum was assessed weekly on alternate leaves of irrigated and non‐irrigated tobacco plants of Kutsaga 51 variety, grown in field plots in 1962‐63. Leaf area, air temperature and humidity within the plots, relative turgidity of the leaves and soil moisture were also measured.Leaves emerged over a period of 37 days. A minimum of 29 days elapsed between leaf emergence and infection; irrigation lengthened this period by 2–6 days for leaves 2–6 and shortened it by 2–10 days for leaves 10–18. The duration of the initial resistant phase, in leaves at comparable stalk positions, appeared to be directly proportional to the eventual size of the leaves at reaping. Leaves were not infected until they were almost fully expanded.The longest dry period, when most irrigation water was applied, occurred when most lower leaves (2–8) were fully expanded and already infected; upper leaves (10–18)w ere then still expanding and not yet infected. Irrigation increased infection in all leaves; it increased the growth of the pathogen during dry weather and the subsequent susceptibility of leaves that were still actively expanding but not yet infected.Irrigation increased the percentage of susceptible leaf area infected, of intact plants, threefold and that of topped plants ninefold. Topped plants had less infection t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03836.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYA Hirst volumetric spore trap, at a height of 30 cm., was used to assess the diurnal distribution ofErysipheconidia in the air in tobacco crops infected with E.cichoracearumin Rhodesia. Air temperature and humidity, and the length of time leaves were wet each day, were also recorded at the same height, amongst the plants. In four seasons, most conidia were caught between 13.00 and 15.00 hr.There were close positive correlations in 1962 between numbers of conidia per m.3 of air per hour and saturation deficit and air temperature during the same hours (10.00–18.00 hr.) Correlations of totalErysipheconidia per day with temperature and humidity were very variable; temperature had no apparent effect during three seasons, but in one (1961)there was a highly significant positive correlation between numbers of conidia and the daily duration of temperatures>25d̀ C. More conidia were also caught when the air was dry for long periods that season, though temperature probably had the greater effect. In 1962, more conidia were caught per day the longer the air was humid (s.D. 0–1 mb.) In 1961, the amount of rain per day had no apparent effect on numbers of conidia, but in 1962 more were caught the greater the daily rainfall. However, rain, which nearly always fell in the afternoon, also removed most conidia from the air that afternoon. Neither windspeed nor duration of leaf wetness appeared to affect spore disper

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb03837.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY