摘要:

SummaryThe infestations of two biotypes ofPanicum miliaceumL. were monitored over a 5‐year period (1981–1985) as they occurred in two townships in southwestern Ontario, Canada. On average, 16·5% of the cultivated fields in Hullett township were infested with the black‐seeded biotype while 12·9% of the fields in North Norwich township were infested with the golden‐seeded biotype. Neither population showed clear signs of increasing. The two biotypes were similar in their ability to persist as adult infestations. The black‐seeded biotype showed a greater potential for colonizing uninfested fields. The crops grown in this region showed different susceptibilities to infestation byP. miliaceum.Corn (maize) fields were susceptible while most grain fields were resistant to infestation. White beans were susceptible to infestation by the black‐seeded biotype. Wheat and oat crops were more resistant to infestation by the golden‐seeded biotype than to those of the black

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00787.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummarySeeds of proso millet (Panicum miliaceumL.) are moved between and within fields on combine harvesters. The dispersal of seeds of two biotypes ofP. miliaceumby combine harvesters was quantified. The golden‐seeded biotype of this weedy annual grass was known to have larger seeds and to experience less seed shattering than the black‐seeded biotype. An average of 3·3% of the seeds on the plants of the black‐seeded biotype was carried more than 50 m by combines, while 0·9% of the golden seeds were carried the same distance. The densities of the seed rain within 50 m of the weedy patches were 3·7 seeds m−2for the black‐seeded biotype and 9·7 seeds m−2for the golden‐seeded biotype. This difference was proportional to the difference in the number of seeds in the respective source patches. The numbers of seeds deposited at various points within 50 m of source patches were close to uniform for both biotypes. There was, however, a significant difference (P<0·05) in the distributions of the seeds o

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00788.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryTreatment of both tolerant and susceptible species with dinitroaniline herbicides results in root swelling typical of mitotic disrupters, however, no root swelling was observed in carrots treated with saturated solutions of all the dinitroaniline herbicides tested, with the exception of oryzalin treatments at ≥ 10−5M. These levels of treatment are 100–1000 times the levels that caused root‐tip swelling, even in tolerant plants. This properly classifies carrot as dinitroaniline‐resistant rather than merely tolerant. Cross‐resistance was noted to the structurally related mitotic disrupter, hexanitrodiphenylamine, and to the structurally unrelated herbicide, amiprophos‐methyl. No resistance was noted to a number of other mitotic‐disrupting herbicides. Both immunofluorescence and electron microscopy indicate that the microtubules of carrot roots were unaffected by dinitroaniline treatment. All organized microtubule configurations (cortical, pre‐prophase bands, spindle, and phragmoplast) were observed in the

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00789.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe effect of isoproturon on the ultrastructure of the photosynthetic apparatus, ribulose bisphosphate carboxylase activity, protein and chlorophyll content, and the grain yield was investigated in two wheat cultivars (Triticum sativumL. cvs Castan and Esquilache) and a weed (Lolium rigidumGaud.). Field experiments used applications of 1–65 and 2–5 kg a.i. ha−1isoproturon post‐emergence, and growth chamber experiments used nutrient solution with the addition of isoproturon (1·7 × 10−4M). The ultrastructure of the photosynthetic apparatus of the cv. Esquilache was much affected by the herbicide. In the case of cv. Castan, slight disorganization of the grana and intergrana was observed. Isoproturon decreased the activity of ribulose bisphosphate carboxylase. A decrease in protein and chlorophyll content was also observed in the cv. Esquilache and inL. rigidum.These alterations were much less evident in the cv. Castan, where, moreover, no loss of protein occurred. The yield of the treated cv. Castan plants was slightly greater than that of the control plants in two consecutive years. However, the yields of the cv. Esquilache were significantly less when the herbicide was applied in the first year at commencement of tillering in a dry season but not when applied at an advanced stage as in the second year in a

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00790.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

RésuméL'étude de la dégradation du propyzamide est réalisée dans 29 sols, dans des conditions de température et d'humidité constantes. Une relation est trouvée entre la vitesse de dégradation et la résistivité des sols. Un apport d'engrais dans les sols entraine une diminution de la résistivité qui se traduit par un ralentissement de la vitesse d

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00791.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe effects of three weeding systems with and without top‐dressed nitrogen were examined in 40 experiments on bread wheat and durum wheat planted by farmers in the Chaouia (semi‐arid area of Morocco) in 1984–1985 and 1985–1986 growing seasons. In both years, hand‐weeding to simulate collection of forage reduced weed numbers by 30% and removed 63% of the weed dry weight. Treatment with 2, 4‐D removed 66% of the weeds and reduced weed dry weight by 82%, in 1985–1986. Hand‐weeding for forage produced 427 kg ha−1weed dry matter in both years, but wheat grain yields were 179 kg ha−1lower than with 2.4‐D treatments. Over both years, the cost of each kg weed forage was 0·43 kg grain yield loss. Without weeding grain yields were 130 kg ha−1lower than 2, 4‐D treatments. Weed control with 2,4‐D increased wheat grain yields over both non‐weeded and hand‐weeded treatments by an average of 154 kg ha−1. Overall, there were no significant effects of nitrogen on wheat or weed yields nor interactions between top‐dressed nitrogen and weeding systems. A total of 157 weed species belonging to 29 botanical families were identified on the 40 experimental sites over both years; 89% were dicotyledons.Papaver rhoeasL. (common poppy), 2, 4‐D susceptible plant, was the most

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00792.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe influence of time of emergence of wild oat (Avena fatuaL.) on its competition with wheat (Triticum aestivumL.) was studied, using boxes that allowed separation of root and shoot competition. The relative yield total for mixtures of wild oat and wheat, grown under different forms of competition and with different wild oat sowing times, was very close to unity, indicating that the two species competed fully for limiting resources. Wild oat was more competitive than wheat when the two species were sown simultaneously, due largely to its greater root competitive ability; the two species had similar shoot competitive abilities. When wild oat was sown 3 or 6 weeks later than wheat, wheat was more competitive than wild oat and the production of wild oat panicles was prevented. This was mainly the result of greater root competitive ability of the wheat, although shoot competitive ability was also greater. The effects of root and shoot competition were additive. It is concluded that in order to prevent the return of wild oat seeds to the soil, and hence obtain long‐term benefit, it is necessary to control the wild oat seedlings emerging within the first 3 weeks after drilling a wheat cro

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00793.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryIn controlled environmental studies, a marked difference was observed between the growth pattern of tomato and eastern black nightshade plants that received doses of 2,4‐D ranging from 28 to 952 g a.e. ha−1. The highest dose of 2,4‐D reduced the dry weight of eastern black nightshade and tomato by approximately 15 and 50%, respectively, when compared with controls. Although the height of both species was reduced by all doses of 2,4‐D, eastern black nightshade plants produced secondary shoots, which compensated for any potential loss in dry weight that otherwise may have occurred. Tomato plants did not produce secondary shoots. After application of14C‐2,4‐D to tomato and eastern black nightshade, the pattern of14C absorption and translocation was similar in both plant species. However, there was significantly more radioactivity recovered in tomato (72%) than in eastern black nightshade (52%) plants, 72 h after treatment. Assay radioactivity in the nutrient solution of hydroponically grown plants indicated that 7·0 and 27·9% of the applied radioactivity was exuded from the roots of tomato and eastern black nightshade, respectively, within 72 h after treatment. Assay of plant extracts by thin layer chromatography revealed that the amount of radioactivity that remained as unaltered 2,4‐D was 73 and 49% in tomato and eastern black nightshade, respectively, 72 h after treatment. Thus the greater tolerance of eastern black nightshade appeared to be due to greater rates of 2,4‐D metabolism and/or greater rates of herbicide elimination

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00794.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryTraditional weeding in slash‐and‐burn agriculture (jhum) in northeastern India involves the retention of a certain proportion of weed biomassin situ.By comparing this weed management practice with total weeding and no weeding, the economic and ecological efficiency of this agroecosystem has been assessed. It is concluded that traditional weeding has little effect on the yield potential of the crop mixture compared with total weeding but it could lead to conservation of soil resources by up to about 20%. Indeed, harvested weed biomass put back into the system is an efficient way of recycling resources under str

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00795.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00786.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY