This summary of biological data is for common milkweed (Asclepias syriaca L.), as a weed in Canada, particularly in eastern Canada. Weedy populations of this perennial occur in great abundance in southern Ontario and Quebec. It belongs to association of plants of roadsides, waste lands and river basins. Recently, this weed has spread into cultivated lands, especially cereals, row crops and forage crops.
De fagon analogue, le glyphosate arrOte la croissance des feuilles sur les talles lorsque seulement la tige principale est trait6e. Cependant, lorsque seules les talles sont trait6es, la production des feuilles n'est pas affect6e sur la tige principale sugg6rant que le produit est mobile dans le phlodme.
Absorption, translocation, and distribution of14C-glyphosate [N-(phosphonomethyl)glycine] were examined in quackgrass [Agropyron repens(L.) Beauv.] plants growing at 10/8, 15/12, and 21/18 C day/night temperatures at 300 μE·m-2·s-1. Absorption of14C-glyphosate followed similar trends in all environments, apart from an initial delay at the highest temperature. Approximately 67% of the applied14C-glyphosate was absorbed after 120 h. Glyphosate translocation to the rhizomes was initially slower in plants growing at 10/8 C than at the higher temperatures, but after 24 h continued at a rate similar to that observed at the higher temperatures. CO2exchange rates (CER) were only slightly influenced by temperature between 5 and 25 C, which may explain the lack of temperature effect on the rate of glyphosate translocation. Approximately 47% of the applied14C-glyphosate was recovered in the rhizomes and associated roots 120 h after application in all environments. Glyphosate accumulated predominantly in new rhizomes under all growing conditions.
Biotypes of several annual broadleaved weeds tolerant to 2-chloro-s-triazines have been recorded, including common lambsquarters(Chenopodium albumL.). The mechanism of resistance in common lambsquarter was based on the differential inhibition of the Hill reaction in chloroplasts by atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Chlorophyll fluorescence and electron transport assays were used with isolated chloroplasts of atrazine-tolerant and susceptible biotypes, to determine the effect of atrazine and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on photosystem II (PS II) activity, differential atrazine penetration of the chloroplast envelope, and relative tolerance to chloro, methoxy, and methylthio triazines. Atrazine and diuron inhibited electron transport on the reducing side of PS II in susceptible biotype chloroplasts. In tolerant biotype chloroplasts only diuron inhibited electron transport whereas atrazine had only slight effects. There were no differences in the chloroplast membrane permeability to atrazine in the two biotypes. Chloroplasts of the atrazine-tolerant biotype of common lambsquarters were also tolerant to the other classes of triazines tested.
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