ABSTRACT Digitaria insularis (L.) Fedde stands out for its resistance to glyphosate and this characteristic may have a relationship with structural alterations. In such context, this research aimed at the characterization of the foliar anatomical structure of two populations of D. insularis (glyphosate-resistant and glyphosate-susceptible biotypes) collected in agricultural areas of Paraná, a Brazilian state. The experiment was conducted at the Laboratory of Botany of the Universidade Estadual do Oeste do Paraná – Unioeste, Brazil. The resistant biotypes of D. insularis differ from the susceptible ones in several structural parameters. Among them, the Mesophyll Thickness in the interveinal region was 7.3% thicker in the resistant biotype, which was also observed in the thickness of the keel, in the percentage of 11.3%, and in the thickness of cuticles in the adaxial surface (TCad), which was 53.8% thicker in the resistant biotype. In this way, we concluded that the resistant biotypes of D. insularis differ from the susceptible ones in several anatomical foliar characteristics, therefore, they present possible mechanisms of resistance to glyphosate.

We had, as an objective, characterizing, anatomically, the leaves of two populations of D. insularis (resistant biotype and susceptible biotype), which were collected in cropping areas in Paraná. In order to do this, a trial design in random sets was employed, which were repeated ten times. To obtain the data, it was evaluated the structural and quantitative variables of foliar blades of anatomical parts, which belonged to different leaves in the mature stage that were removed from distinct resistant and susceptible biotypes of D. insularis. The structural variables of the cross-sectional parts evaluated from the foliar blades were: the thickness of the foliar blade in the intercostal region (TBI); thickness of the keel (TK); stomata number (SN) and thickness of cuticle (TC) in the adaxial and abaxial faces. The resistant biotypes of D. insularis differ from the susceptible ones in several structural parameters, among them, there is the foliar blade in the interveinal region that was 7.3 ticker in the resistant biotype, which was also observed in the thickness of the keel, in the percentage of 11.3%, and in the thickness of the cuticle in the adaxial face (TCD), which was 53.8% thicker in the resistant biotype. In this way, we concluded that the anatomical foliar characteristics observed in the resistant biotypes, which differ from the susceptible ones, can be related to the reduction in the absorption and the herbicides translocation speed, constituting, therefore, possible mechanisms of resistance to glyphosate

Tivemos como objetivo caracterizar anatomicamente as folhas de duas populações de D. insularis (biótipo resistente e biótipo suscetível) coletadas em áreas agrícolas no Paraná. Para isso, utilizou-se delineamento experimental em blocos ao acaso, com dez repetições. Para a obtenção dos dados, foram avaliadas variáveis estruturais quantitativas de secções anatômicas da lâmina foliar, pertencentes a diferentes folhas no estágio maduro retiradas de distintos biótipos resistentes e suscetíveis de D. insularis. Entre as variáveis estruturais das secções transversais da lâmina foliar avaliadas foram: espessura da lâmina foliar na região intercostal (ELI); espessura da quilha (EQ); número de estômatos (NE); espessura da cutícula (EC) nas faces adaxial e abaxial. Os biótipos resistentes de D. insularis diferem dos susceptíveis em vários parâmetros estruturais, entre eles, quanto a lâmina foliar na região internervural que foi 7,3% mais espessa no biótipo resistente, o que também foi observado na espessura da quilha com 11,3% e na espessura da cutícula na face adaxial (ECD) que foi 53,8% mais espessa no resistente. Dessa forma, concluímos que as características anatômicas foliares observadas nos biótipos resistentes que diferem dos susceptíveis, podem estar relacionadas com a redução na absorção e na velocidade de translocação de herbicidas, constituindo assim possíveis mecanismos de resistência ao glyphosate.

Resumo O objetivo deste trabalho foi avaliar o efeito da palhada de aveiapreta (Avena strigosa) sobre o período anterior à interferência (PAI) de plantas daninhas na cultura da cenoura 'Alvorada' (Daucus carota). O experimento foi realizado em delineamento de blocos ao acaso, em arranjo fatorial 2×5, com cinco repetições. Os dois seguintes fatores foram avaliados nos anos de cultivo de 2016/2017 e 2017/2018: cobertura de solo com e sem 10 Mg ha1 de palhada de aveia-preta; e períodos de coexistência com as plantas daninhas – 0, 15, 30, 60 e 120 dias após a emergência (DAE). Para determinar o PAI, considerou-se como aceitável a perda de 5% na produtividade comercial de raízes da cenoura. Ao final do ciclo da cultura, a palhada reduziu a massa seca total de plantas daninhas em 43,5 e 67,5%, respectivamente, no primeiro e no segundo ano de cultivo. O PAI dos cultivos com e sem palhada foi, respectivamente, de 2,0 e 1,5 DAE no primeiro ano e de 17 e 6,0 DAE no segundo. O uso da palhada de aveia-preta aumenta o PAI para cultura da cenoura 'Alvorada'.

Abstract The objective of this work was to evaluate the effect of black oat (Avena strigosa) straw on the period prior to the interference (PPI) of weeds in the 'Alvorada' carrot (Daucus carota) crop. The experiment was carried out in a randomized complete block design, in a 2×5 factorial arrangement, with five replicates. The following two factors were evaluated in the 2016/2017 and 2017/2018 crop years: soil cover, with and without 10 Mg ha1 black oat straw; and periods of coexistence with weeds – 0, 15, 30, 60, and 120 days after emergence (DAE). To determine the PPI, a loss of 5% in the commercial yield of carrot roots was considered as acceptable. At the end of the crop cycle, straw reduced the total dry mass of weeds by 43.5 and 67.5%, respectively, in the first and second crop years. The PPI of the crops with and without straw was, respectively, 2.0 and 1.5 DAE in the first crop year and 17 and 6.0 DAE in the second. The use of black oat straw increases the PPI for the 'Alvorada' carrot crop.

Resumo: O objetivo deste trabalho foi avaliar o efeito da competição de plantas daninhas sobre o acúmulo de nitrogênio e fósforo nas folhas e sobre a massa seca das raízes de mandioca (Manihot esculenta), nos sistemas convencional e direto, em dois ciclos de cultivo. Os experimentos foram realizados em delineamento de blocos ao acaso, com parcelas subsubdivididas e quatro repetições. As parcelas consistiram do plantio convencional ou do plantio direto; as subparcelas, da competição ou não com plantas daninhas; e as subsubparcelas, dos períodos de avaliação (0, 25, 50, 75, 100, 125, 150, 175, 200 e 225 dias após o plantio/poda). No primeiro ciclo, a competição com plantas daninhas reduziu o acúmulo de nitrogênio em 82,6 e 81,3% e o de fósforo em 65,7 e 85,3%, no plantio convencional e no plantio direto, respectivamente. No segundo ciclo, as reduções no acúmulo de nitrogênio foram de 41,1 e 52,4% e, no de fósforo, de 44,1 e 52,6%, no plantio convencional e no plantio direto, respectivamente. A massa seca das raízes de mandioca cultivada sob competição de plantas daninhas apresentou reduções de 15,8 e 11,2% no plantio convencional e no plantio direto, respectivamente, apenas no segundo ciclo. A competição de plantas daninhas reduz o acúmulo de nitrogênio e fósforo nas folhas de mandioca, nos sistemas convencional e plantio direto, em ambos os ciclos de cultivo, mas reduz a matéria seca das raízes de mandioca apenas no segundo ciclo.

Abstract: The objective of this work was to evaluate the effect of weed competition on the accumulation of nitrogen and phosphorus in the leaves and on the dry weight of the roots of cassava (Manihot esculenta) in the conventional and no-tillage systems, in two crop cycles. The experiments were carried out in a randomized complete block design, with split-split plots and four replicates. The plots consisted of conventional tillage or no-tillage; the split plots, of the competition or not with weeds; and the split-split plots, of the evaluation periods (0, 25, 50, 75, 100, 125, 150, 175, 200, and 225 days after planting/pruning). In the first cycle, weed competition reduced the accumulation of nitrogen in 82.6 and 81.3% and of phosphorus in 65.7 and 85.3% under conventional tillage and no-tillage, respectively. In the second cycle, the reductions in the accumulation of nitrogen were of 41.1 and 52.4% and of phosphorus of 44.1 and 52.6%, in conventional tillage and no-tillage, respectively. The root dry weight of cassava grown with weed competition showed reductions of 15.8 and 11.2% under conventional tillage and no-tillage, respectively, only in the second cycle. Weed competition reduces the accumulation of nitrogen and phosphorus in the leaves of cassava in the conventional and no-tillage systems in both crop cycles, but reduces the dry matter of cassava roots only in the second cycle.