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A influência de concentrações de bispyribac-sodium, aplicadas na parte aérea ou nas raízes das plantas de arroz, foi avaliada. O experimento foi realizado em casa de vegetação, usando bispyribac-sodium nas doses de 0, 24, 48, 72, 96 e 120 ppb, aplicadas na parte aérea ou nas raízes de plantas de arroz BRS Pelota e BRS Bojuru. As unidades experimentais constaram de copos plásticos perfurados na lateral próximo ao fundo, com areia lavada, onde foram colocadas cinco sementes de arroz, e mantidas dentro de bandejas contendo água em nível imediatamente inferior ao nível de areia. Quando as plantas se encontravam no estádio de duas a três folhas definitivas, as soluções foram pulverizadas diretamente sobre as folhas. Para aplicação nas raízes, o herbicida foi colocado na água de irrigação. Quarenta dias após emergência, foram avaliados comprimento de plantas, matéria fresca e seca de parte aérea e raízes e volume do sistema radical. Os dados foram submetidos à análise de variância, com análise de regressão através de modelos polinomiais, quando significativos. O cultivar de arroz BRS Bojuru se mostrou mais sensível que o BRS Pelota ao incremento na dose de bispyribac-sodium, com efeito mais pronunciado quando aplicado diretamente às folhas. Em campo, devem-se evitar doses acima das recomendadas, principalmente quando do uso de cultivares japonica. The aim of this work was to evaluate the influence of bispyribac-sodium concentrations applied to shoot and roots of rice plants. The trial was conducted under controlled environment, using bispyribac-sodium at 0, 24, 48, 72, 96 and 120 ppb, applied to shoot or roots of rice plants cvs. BRS Pelota and BRS Bojuru. The experimental units were composed of plastic bottles with 500 mL capacity, drilled in the lateral next to the bottom, filled with washed sand, where five seeds were sowed, and the experimental units were put into a basin containing water at a lower level than the sand in the experimental units. The solutions were directly sprayed on the leaves, or mixed to the irrigation water when applied to the roots. Forty days after emergence, plant length and fresh and dry weight were evaluated in the shoots and roots, as well as root volume. The data were submitted to analysis of variance by the F-test and polynomial regression was drawn in case of significance. Cultivar BRS Bojuru was more sensitive to increasing rates of bispyribac-sodium than BRS Pelota, when applied to the leaves. Rates above the recommended should be avoided under field conditions, mainly when using japonica cultivars.

In this thesis, two phenomenon related to herbicide physiology were investigated, resistance and antagonism. The resistant (R) and susceptible (S) biotypes of hemp-nettle ('Galeopsis tetrahit') were found in Alberta. Dose-response experiments revealed that the resistance ratios were 3, 8, 1.7, 1.6, 0.7 and 0.6 in response to MCPA, fluroxypyr, dicamba, 2,4-D, glyphosate and chlorsulfuron, respectively. The uptake of [14C]MCPA was not different in R and S, however, 45% and 58% of the absorbed 14C was exported from the treated leaves, with 32 and 38% moving to the roots in R and S, respectively, 72 hours after treatment (HAT). In the root, 55 and 42% of the recovered 14C was MCPA metabolites in R and S, respectively. A lower amount of MCPA translocation along with a higher rate of metabolism in the roots may protect the hemp-nettle R biotype from MCPA injury. The MCPA-resistance trait is nuclear encoded, and probably governed by at least two genes with additive effects. The addition of Na-bentazon to tritosulfuron (482.5 and 10 g ai ha -1, respectively) plus DASH HC (0.156%) reduced tritosulfuron toxicity to white bean ('Phaseolus vulgaris' L.) by 86% (i.e. antagonism ratio [AR] was 1.86). Addition of (NH4)2SO4, (NH4)2HPO4 or NH4NO3 (0.2 N) to the aforementioned mixture eliminated the antagonism (ARs were 1.2, 1.1 and 1.2, respectively), while addition of NH4CH3 COOH did not (AR 2.0). Replacing Na-bentazon with NH4-bentazon or H-bentazon (471.4 and 532 g ai ha-1, respectively) eliminated the antagonism (AR 1.1 and 1.1, respectively). Addition of 0.2 N Na2 SO4 or NaCH3COOH to mixtures that contained NH 4-bentazon resulted in ARs of 1.20 and 1.95, respectively. DASH at 0.625%, or separate applications of Na-bentazon and tritosulfuron reduced the antagonism. Na-bentazon caused 60% and 80% reduction in the uptake and the translocation of [14C]tritosulfuron, respectively. The addition of (NH 4)2SO4, replacement by NH4-bentazon or DASH (0.625%) eliminated Na-bentazon antagonism on [ 14C]tritosulfuron uptake but did not affect the translocation of tritosulfuron. Scanning electron microscopy revealed that a mixture of Na-bentazon, tritosulfuron plus DASH formed a layer of grainlike crystals on the leaf surface, whereas, the addition of (NH4)2SO4 or replacement with NH4-bentazon resulted in an amorphous deposit.