摘要:

Summary:The genetic diversity and clonal structure of weedy and non‐weedy populations of a clonal perennial,Rubia peregrinaL., were investi gated in a vineyard and in unmanaged habitats of Southern France. The overall genetic diversity of populations was evaluated on a large scale, whereas spatial distribution and clonal structure were studied on a small scale. Isozyme phenotypes were identified using electrophore‐sis of three polymorphic enzyme systems. Most isozyme phenotypes were restricted to one population. Intra‐population genetic diversity did not differ between populations, whereas clonal structure did. In the vineyard, few clones forming numerous packed ramets and with dis tinct areas were identified, whereas in the unmanaged habitats a higher number of inter mingled clones, forming few widely spaced ramets, were observed. The variability in clonal structure may be linked to different responses of clones to the contrasting environmental condi tions. These results suggest that the colonizing ability of a clonal perennial weed is not necessarily associated with low levels of genetic diversity, but may be related to the variability of the clonal stru

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01764.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:The concentrations of haloxyfop in nutrient solution required to reduce the total plant dry weight of soybean (Glycine maxL. Merr. ‘Evans’), red fescue (Festuca rubraL. ‘Pennlawn’), and tall fescue (Festuca arundinaceaSchreb. ‘Houndog’) by 50% (GR50) were determined. The GR50) values for soybean, red fescue and tall fescue were 76 μM, 3μM and 0.4 μM, respectively. The reduction in growth in roots and shoots of soybean was similar. In contrast, the relative reduction in root tissue weight was greater than that for foliar tissue in both grass species. The amount of14C‐haloxyfop in soybean roots or shoots was higher than in red fescue or tall fescue. Red fescue accumulated less haloxyfop in the foliage than in the roots. On the other hand, similar amounts of14C‐haloxyfop accumulated in both organs in both soybean and tall fescue.14C‐haloxyfop appeared to be actively absorbed by the roots of all species. Soybean absorbed more nutrient solution, but utilized it less on a per gram dry matter produced basis than the grass species. Differences in the uptake and translocation of haloxyfop by roots do not account for differences in tolerance between species. However, a higher level of retention of haloxyfop in the roots of red fescue than in tall fescue may provide the former with an additional selectivity advantage under conditions where there is significant root expos

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01765.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:The longevity of buriedRottboellia cochinchinensis(Lour.) W.D. Clayton seed represents a major survival mechanism for the weed, enabling the persistence of a continuing source of weed seeds in crop land. The pattern of seed persistence and depletion ofR. cochinchinensisin cultivated maize soils was investigated by means of (1) studies on the effect of depth and duration of burial on the viability of the weed seeds, (2) quantitative estimation of the seed population and viability in cultivated fields, and (3) the periodicity of emergence and effects of cultivation on seed germination both in the field and in the greenhouse. The results indicated that the mode of persistence was innate (8.5%) and enforced (35%) dormancy after 1 year of burial, and that the persistency component of the seed population on cultivated soils ranged from 40.60%. The weed was able to remain viable at depths of 45 cm, indicating an excellent mechanism of escaping the effects of most soil‐applied herbicides, and it was shown that tillage increases the depletion rate of the weed seed reserve by 32% per yea

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01766.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Homoclime analysis of three weed species of potential significance to agriculture in New Zealand was undertaken. Using the Bio‐climate Prediction System computer program (BIOCLIM), climatically suitable regions in New Zealand were estimated forHomeria flaccida Sweet, Chondrilla junceaL. andEmex australisSteinh., on the basis of their respective distributions in Australia. These estimates indicated that the current eradication campaign forHomeriais warranted, owing to the existence of extensive areas with a suitable climate on both of New Zealand's main islands. ForHomeria, most of the known occurrences fell within regions predicted to be climatically suitable. ForChondrilla, only very small areas were predicted to be climatically suitable, due to the generally low temperatures that prevail during its reproductive period. This suggests that the designation ofChondrillaas a quarantine pest may be unwarranted. Much of the land in the interior of the North Island was estimated to be climatically suitable for Emex. However, invasion has not occurred, despite the presence of this weed in New Zealand for over 100 years. The failure ofEmexto invade perennial pastures is probably a result of its poor competitiveness, since climatic and edaphic characteristics appear to be suitable over large areas. It is concluded that homoclime analysis can be used to identify regions at risk of invasion by a species which has been weedy elsewhere, when potentially modifying factors such as soils, land use/management practices and competitive interactions are taken into accoun

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01767.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Seeds of four winter wheat cultivars, Slejpner, Galahad, Avalon and Penman, were sown at depths ranging from 6–75 mm in soil in pots, and isoproturon or chlorotoluron was then applied to the soil surface. For chlorotoluron‐treated plants (both pre‐ and post‐emergence) the dose required to produce a 50% effect (ED50) was unaffected by depth of planting. In contrast, for isoproturon applied pre‐emergence, the ED50for both Avalon and Slejpner was strongly affected by sowing depth. Although chlorotoluron was much more active in a second experiment when applied post‐emergence to Slejpner wheat, the ED50for both herbicides increased with greater depth of sowing. Protection of wheat from isoproturon damage by deeper planting was enhanced if the adsorption capacity of the soil was raised from Kd0.5 to 2.0 by incorporation of activated charcoal in the soil. Isoproturon entry into plants (as measured by the effect on rate of photosynthesis) was slower in those that had been sown deeper and were growing in more adsorptive soils, but there was no obvious relationship between these observations and isoproturon distribution in the soil profile. In nutrient culture the four wheat cultivars responded similarly to a range of doses of isoproturon. The chlorotoluron‐sensitive cultivars, Slejpner and Galahad, were damaged by much lower doses of chlorotoluron than were Avalon and Penman.Bromus sterilisL. responded similarly to wheat with regard to its interaction with isoproturon and planting depth.Alopecurus myosuroidesHuds., however, was less damaged by isoproturon when the zone above the seed was protected from the herbicide by growing the shoot through a

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01768.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Chlorimuron ethyl uptake into excised soybean root tissue was investigated using14C‐labelled herbicide. Chlorimuron ethyl accumulated in the root tissue, reaching a maximum concentration after 2 h and then declining over the next 2 h. The herbicide did not accumulate against a concentration gradient. The tissue concentration was linearly correlated with the external herbicide concentration. The Q10between 15 and 25°C was 1.6. Addition of KCN and anoxia reduced uptake. The efflux of14C that had accumulated in root tissue segments occurred in two phases: a rapid phase with a T½ value of 6.3 min and a slower phase with a T½ value of 172 min. Chlorimuron ethyl uptake and efflux in excised soybean root tissue closely resembled that previously observed in velvetleaf, a sensitive weed spe

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01769.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:The competitive interactions betweenAvena sterilisssp.ludoviciana(Dur.) Nyman and winter barley have been studied, taking into consideration the densities of both species. As the density of A.sterilisincreased, barley yield decreased exponentially. A 10% reduction in yield was found with wild oat densities ranging from 20–80 panicles m–2, and yield losses reached 50%, with densities of>300 panicles m–2, Barley grain yield was reduced by wild oats through a reduction in the number of fertile tillers. Climatic conditions during the growing seasons affected the response of barley to wild oat competition. In general, barley yields were relatively unaffected by seeding rates, with similar responses observed in the presence and in the absence of wild oat infestations. However, the highest yield losses were obtained with the lowest seeding rate (100 kg ha–1). Furthermore, low barley densities allowed the wild oat plants to produce more seeds, increasing the potential infestation during the following

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01770.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Résumé:L'alcoolyse du chlorsulfuron (méthanol, étha‐nol) implique seulement la fonction urée de la molécule. La formation de carbamate permet de postuler l'existence d'isocyanate intermédiaire. Deux voies de dégradation sont observées au cours de l'hydrolyse du chlorsulfuron en solution aqueuse acide: hydrolyse de la fonction urée et hydrolyse du substituant méthoxy. L'augmentation de la température (25 à 55°C) favorise la vitesse de conversion et l'hydrolyse de la fonction urée. L'abaissement du pH (6 à 2,4) accé1ère fortement le processus et diminue son énergie d'activation sans en modifier la sélectivité. Les effets d'autres facteurs (cations de métaux de transition, argiles) demeure

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01771.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY