摘要:

AbstractThe presence of the fish speciesCyprinus carpioL.,Tilapia niloticaL. andPuntius gonionotusBleeker in irrigated paddy fields resulted in a reduction of the numbers of sedges and broadleaved weeds at low water levels around 5 cm. On the contrary, weed growth was enhanced at higher water levels. Similar results were obtained for the percentage area covered and the speciesMarsilea crenata. At low water levels the number of uprooted weeds in rice‐fish fields was markedly increased if compared to control fields. This indicates that fish prefer shallow areas of rice fields with more abundant food supplies as a feeding place. In rice‐fish fields the water was turbid on77.8% of the test plots (1 m2) compared to only 47.4 % on the control fields. The findings are explained by the combined action of a ‘fertilizing effect’ and a ‘feeding effect’, both of which are

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00918.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractScreening for persistence inLolium perenneL.The assessment of persistence, as well as yield potential, is fundamentally important for cultivar evaluation of perennial grasses. But it is difficult to estimate the persistence because of limited time available for testing new varieties. The aim of this study was to find out conditions for effective and quick selection for persistence inLolium perenne.Four strains ofLolium perennewere investigated for three years in the following split pot design with 3 replications: 180–220 kg N/ha or 360–440 kg N/ha and year, 3 or 6 cuts/year and 3–4 cm or 7–8 cm cutting height.Yield, regrowth (score 0–9, 7 days after each cut) and persistence (number of non‐surviving ramets) were determined for each ramet of all clones and for each plot of the strains. The dry matter yield was reduced to about 50 % between the first and the third year of the investigation. The differences in the dry matter yield between the four strains have been more evident in the six than in the three cutting treatment.Already at the end of the first year of the investigation the strains differed significantly in the regeneration in the six cut treatment. The regrowth of strain III showed a significant reduction compared with the other three strains.A significant reduction of the surviving ramets was first observed at the end of the second year of the investigation in the six cut treatment only, but between the strains were no significant differences.These results demonstrate, that an investigation on single plants over a period of three years cannot give an exactly prediction about the persistence ofLolium per

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe harvest index Z is defined, for example for cereals, as the ratio between grain yield X and biological yield Y: Z = X/Y. In this paper the character associations among biological yield, grain yield and harvest index have been investigated theoretically by calculating the covariances and correlation coefficients between harvest index and grain yield and, additionally, between harvest index and biological yield. Explicit formulae are derived for these covariances and correlation coefficients and conclusions are derived and discussed. Many facts and relations among these characters which are well‐known and frequently established by many experimental studies with quite different crops can be obtained and characterized by these theoretical investigations as necessary implications of the underlying statistical relationships.Finally, all the theoretical studies and results are demonstrated and applied to a numerical example of winter‐rapeseed d

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to compare responsiveness to environment as well as the stability of newly developed promising lines with traditional commercial cultivars. Subject research was conducted in Ankara between 1983‐1989 on common and durum wheat cultivars and lines. Regression coefficient (b) was used as the criterion of genotypes' responsiveness to environment whereas deviation from regression (S2d) and coefficient of determination (r2) were used as stability parameters. Each experiment year was regarded as an environment and yield average of each year was used as the environmental index.In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological region

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractResults reported in the literature with regard to productivity of intercropping systems in comparison to sole cropping are very inconsistent. A field experiment was therefore conducted in the northern part of the Guinea Savanna in Ghana to compare the productivity of maize/cowpea mixed cropping, maize/cowpea relay intercropping with maize/cowpea rotation and maize monocropping over a 4‐year period. The treatments included two levels of nitrogen (0 and 80 kg of N ha−1y−1as urea) and two levels of phosphorus application (0 and 60 kg of P ha−1y−1as Volta phosphate rock). At all levels of N and P application, maize yields of the intercropping systems, especially of maize/cowpea mixed cropping, were significantly lower than in sole cropping. Highest maize yields were obtained in maize/cowpea rotation, which in contrast to the other cropping systems did not show any reductions in yields over years. Cowpea yields were generally less affected by the cropping system, but were notably depressed when cowpea was relay‐intercropped with maize. In treatments without fertilizer application (N and P) Land Equivalent Ratios (LER) and Area x Time Equivalency Ratios (ATER) generally indicated lower productivity of the intercropping systems as compared to sole cropping, with the maize/cowpea rotation showing the highest productivity. Conversely, fertilizer application resulted in higher productivity of the intercropping systems over the 4‐year period. Productivity on the basis of ATER was generally lowest in maize/cowpea relay‐intercropping as a consequence of the long time of land occupation. All of the parameters indicate low productivity of maize monocropping, clearly demonstrating that crop sequence as well as fertilizer application must be considered as important for maintaining high production leve

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractDevelopment of amyloplasts and starch synthesis in seeds of field and garden peasAmyloplast development and changes in starch and amylose content in seeds of field and garden peas (Pisum sativumssp.sativumand ssp.medullare)was studied from flowering to maturity in view of a possible relationship between amyloplast form and starch composition.Starch and amylose contents increased at different rates in both subspecies. In field peas starch content had reached the maximum (44 % in DM) 26 days after flowering with 45 % amylose in total starch. In garden peas, 25 days after flowering, starch content had only reached half of its maximum (32 % in DM) with an extremely high amylose proportion (88 %). At that growth stage form and size of amyloplasts were similar in both subspecies. There seems to be no tight relationship between form of amyloplasts and proportion of amylose in total starch.But then, when amyloplasts abruptly increased in size those of garden peas disrupted suddenly. This disruption is not due to a high amylose content. Because in a cross‐breeding of field and garden peas, which was also investigated, the amyloplasts had remained intact irrespective of a high amylose proportion (63 %). The disruption may be due to differences in arrangement of starch molecule and in structure of plastid envelop

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00923.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo annual ryegrass (Lolium multiflorumLam.) cultivars differing in Al sensitivity were grown in nutrient solution at pH 4.2 to assess the effects of temperature (10/6 and 22/18 °C day/night), Mg (0.1 and 1 mM) and Al solution concentrations (0, 3.7 and 74μM) on several factors influencing grass tetany potential of forage. Added Al depressed Mg and Ca shoot concentrations and increased shoot K/(Ca + Mg) equivalent ratio especially after prolonged treatment at higher temperature and lower Mg solution concentrations. These effects were more pronounced in the relatively Al‐sensitive cultivar Wilo which appeared to be less Mg‐efficient as well. Grass tetany potential will therefore be higher following a temperature rise if Al‐sensitive ryegrass is grown in a medium containing low Mg and high Al

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00924.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractSoil application of different formulations of carbofuran at 3.0 and 1.5 g.a.i. metre row−1did not have any impact on vigour and viability of the resultant seeds of sorghum. Fresh seeds from encecap ‘A’, encecap ‘B’ and furadan treated plots contained higher residues than the permissible limits and in artificially aged seeds the quantities were below the permissible limits. The degradation was evident with the growth and development of seedlings grown from fresh and aged seeds. Residues from lower doses dissipated faster than higher doses. The general decline in percentage germination and vigour could not be attributed to the residual toxicity but only to the ageing

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00925.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Books Reviewed in this Article:Osborne, Daphne J. and Jackson, M. B. (Eds.): Cell Separation in Plants – Physiology, Biochemistry and Molecular BiologyHaug, G., and H. Hoffmann, Chemistry of Plant Protection. Managing eds., W. S. Bowers, W. Ebing, T. R. Fukuto, D. Martin, R. Wegler, I. Yamamoto (eds.). Vol. 2. Degradation of Pesticides, Desiccation and Defoliation. ACh‐Receptors as Targets.Brücher, H.: Useful Plants of Neotropical Or

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1991.tb00926.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY