摘要:

SummaryThe data on seed population dynamics of three weedy species ofEupatorium, viz.E. adenophwrumSpreng.,E. ripariumRegel andE. odoratumL. have been presented and discussed in the paper. The seed production and seed populations in soil seed bank were estimated, and the fate of buried seeds in soil was followed over a 2‐year period. All the three species ofEupatoriumproduced a large number of seeds. The seed production ofE. ripariumper unit area was higher than that of the other two species because of its high population density. In all the three species most of the seeds were found to be present in the top 2 cm of the soil. The viable seed population of the three species ofEupatoriumdeclined exponentially alter their burial in soil showing almost similar mortality patterns. A large proportion of seeds of all theEupatoriumspp. remained under enforced dormancy during their burial in soil with only a small fraction exhibiting induced dormancy. The longevity of the buried seeds increased on account of the dormancy imposed on them. The loss of seeds through degeneration and/or decomposition was rather lo

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryEupatorium adenophorumSpreng. is an important weedy colonizer in early successional communities developing after slash and burn agriculture (jhum) at higher elevations of the north‐eastern hill regions of India. The relative performance of this species in terms of fecundity and survivorship in successional plant communities has been worked out. A net population increase occurred through both vegetative and sexual reproduction in early successional fallows up to 6 years old, the increase being greatest in a 6‐year fallow. Mortality of seedlings was high in 1‐ and 3‐year fallows, low in a 6‐year fallow but reached 100% in older fallows. Seedling mortality was maximal during the monsoon although some seedlings also died during winter as a result of drought and frost. Mortality of vegetative sprouts followed a similar pattern to that of seedlings. The reproductive potential was reduced with increasing age of the successional communities and in a 15‐year fallow all individuals were non‐reproductive. SinceE. adenophorumis able to succeed only in fallows of less than 6 years, repeated short jhum cycles of 4–5 years have had the effect of arresting succession al

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

RésuméDivers herbicides ont été administrés à des plantules de concombres de 17 jours, croissant sur solution nutritive. Les activités des peroxydase, catalase et glycolate oxydase ont été mesurées après 1, 2 et 3 jours dans les feuilles des plantules traitées avec des doses létales d'atrazine, de chlortoluron, de MCPA, d'alachlore et de dichlobenil. Les mêmes déterminations ont été effectuées après 5 h sur plantules préalablement pulvérisées au paraquat et au DNOC. L'atrazine et le chlortoluron ont inhibé l'activité de la peroxydase et stimulé légèrement celle de la catalase. Ces deux enzymes ont été activées par le MCPA, l'alachlore et le dichlobenil et après 3 jours, les rapports peroxydase/catalase ont été respectivement de 0.7; 7 et 14. Le DNOC et le paraquat ont inhibé la catalase. L'activité de la glycolate oxydase a augmenté dans les plantules traitées à l'atrazine, au chlortoluron, au MCPA et au DNOC et a diminué dans celles

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryThe combined effects of 0, 1 and 2 ppm trifluralin and five soil salinity levels (0.35, 2, 4, 6 and 8 mS/cm) on growth and chemical composition of soybeans [Glycine max(L.) Merr.] were studied in a glasshouse experiment. Analyses of variance indicated that the interaction of soil salinity and trifluralin was not significant for root and top dry weights and root nodulation. Root dry weight was not affected by trifluralin, whereas 2 ppm trifluralin significantly reduced top dry yield and root nodulation. Shoot and root yields and root nodulation were reduced with increasing soil salinity.Trifluralin at 1 ppm significantly decreased P concentration and at 2 ppm substantially increased N concentration. Moreover, there was a general trend of an increase in N concentration and a decrease in P concentration with salinity.The concentration and uptake of Cl and Na increased with increasing soil salinity. Probably large accumulations of Cl and Na and/or water stress caused by high salinity were responsible for growth reductions in salinized media.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ZusammenfassungIm humiden Nordwesten Tunesiens wurden mit Hilfe von pflanzensoziologischen und bodenkundlichen Untersuchungen unter Einbeziehung von bereits vorliegenden Bewirtschaftungsdaten die Ursachen der Verunkrautung auf neuangelegtem Grünland untersucht. Die Jahr‐zu‐Jahr‐Schwan‐kung der Verunkrautung ist sehr verschieden. Hingegen verandert sich der Jahresgang der Verunkrautung kaum von Jahr zu Jahr.Die Ursachen fur die Verunkrautung der Klee‐Gras‐Weiden, die auf den sandigen Boden deutlich starker ist, als auf den schweren Boden, ergeben sich aus der Unzuläanglichkeit des Standorts, insbesondere aber aus einer Vielzahl von Bewirtschaftungsfehlern. Gefördert wurde die Verunkrautung u.a. durch: (1) Die ungünstige Niederschlagsverteilung in den Jahren 1970/71, 1972/73 und 1973/74; (2) Weideverfahren mit holier Besatzdichte, kurzer Freβzeit und langerer Ruhezeit; (3) Achtlose Weideführung auf winterlich übernäβten Boden; (4) Unkrautbekämpfungsmaβnahmen mit ungeeigneten Herbiziden; (5) Verschiedene Schädlinge und Krankheiten, die bevorzugt den Klee befallen.Die Verunkrautung der mehrjährigen Mäh‐weiden mitFestuca arundinaceaist nicht sehr ausgeprägt und nimmt, bedingt durch den jährlichen Schnitt im Frühjahr, über die Jahre merklich ab. Nach dem Schnitt stellt sich kurzzeitig eine sehr spezifische Verunkrautung mit ausdauernden Pflanzen ein. Es werden Vorschläge zur Einschrankung der Verunkrautung durch Haltung

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00149.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryAs was described in a previous publication, the influence of a number og herbicides and herbicide mixtures which are being used for the post‐emergence control of weeds in maize on the Transvaal Highveld, have been tested for their efficiency in the control of problem weeds. Both the percentage mortality and percentage dry mass difference between the test plants and the controls 10 days after application of the respective herbicides were used as bioassay methods.Datura stramoniumL. was very susceptible to most of the herbicidal treatments up to the nine‐leaf stage. The reason why it is considered a problem weed should perhaps be sought in the erratic germination of its seeds over a number of years, thus evading common practices of weed cont

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummarySixteen different herbicides and herbicide mixtures were evaluated for their efficiency in controllingCrotalaria sphaerocarpaPerr. ex. DC. using percentage mortality and relative plant dry mass as criteria of herbicide efficiency. Paraquat and a mixture of atrazine and Tronic were the only treatments which effectively controlled the weed at all ten leaf stages tested. Atrazine alone and ametryne alone were 100% effective only for the first four leaf stages. Other treatments were relatively ineffective.The wax coat on the leaves ofC. sphaerocarpapossibly impedes the absorption of lethal quantities of some herbicides, resulting in an apparent resistance. This phenomenon, probably accounts for the fact that this plant is considered to be a problem weed.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryExperiments with the alkaline heavy clays of the Sudan Gezira showed that when the strigol analogue GR7 was applied to moist soil prior to subjectingStriga hermonthicaseeds to moist conditions (‘conditioning’) for 7–14 days, there was no significant increase in germination. Conditioning of seeds in soils treated with GR7 had an adverse effect on the responsiveness of seeds when GR7 was added again after conditioning. Under ideal conditions, when GR7 was applied to conditioned seeds in moist soil, up to 75% germination could be induced by 2.0 kg/ha incorporated to 2–3 cm depth. Residual activity of GR7 persisted in air‐dry soil, but at 50% moisture there was complete loss within 1 day. However, when conditioned seeds were put into the soil immediately after GR7 application its activity increased with increasing soil

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryUnrestricted weed growth resulted in serious yield losses (60–75%) in rice (Oryza salivaL.). Hand‐weeding once at 2 weeks after crop emergence was ineffective, but weeding at 2 and 2 weeks after crop emergence brought yield losses down to 20%. Pre‐emergence application of bifenox and oxadiazon (12 l) and post‐emergence application of molinate + propanil gave crop yields comparable to that of the clean weeded control (91–129%). Grain yields obtained with pre‐emergence application of oxadiazon (25 EC) and post‐emergence applications of propanil, bentazone + propanil, and bifenox alone or as a tank mix with propanil or bentazone were considerably less than those obtained from the clean weeded plots. Bifenox, oxadiazon (12 l) and propanil + molinate gave adequate and persistent weed control (72–97%), and did not damage rice. Oxadiazon (25 EC) gave good weed control but resulted in a serious stand reduction. Post‐emergence application of propanil, propanil + bentazone bifenox alone or as a tank mix with propanil or bentazone had no adverse effect on crop stand, but gave poor control o

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1982.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY