Alterações anatômicas foliares em plantas de Brachiaria subquadripara submetidas à aplicação de herbicidas

Abstract

RESUMO -O presente trabalho teve por objetivo avaliar a eficiência do controle dos herbicidas diquat, glyphosate e imazapyr e as alterações anatômicas do limbo foliar provocadas por eles em plantas de Brachiaria subquadripara. As plantas foram cultivadas em caixas-d'água sob condições de campo e, quando atingiram estádio de pleno desenvolvimento vegetativo, foram pulverizadas com soluções de diquat a 400 g ha -1 , glyphosate a 4.320 g ha -1 em associação com o adjuvante Aterbane a 0,5% v v -1 e imazapyr a 750 g ha -1 . Além disso, utilizou-se uma testemunha sem aplicação de herbicida. Foram realizadas avaliações de controle e das seguintes características anatômicas quantitativas das regiões da nervura central e da internervural do limbo foliar, além da região do colmo: porcentagem da epiderme adaxial e abaxial, porcentagem da endoderme, porcentagem do feixe vascular, porcentagem de lacunas do aerênquima, porcentagem de parênquima, espessura foliar, porcentagem da epiderme do colmo, porcentagem do câmbio vascular e diâmetro do colmo. Os herbicidas diquat e imazapyr promoveram o maior número de alterações nos caracteres anatômicos quantitativos das regiões da nervura central e internervural do limbo foliar e da região do colmo das plantas. Contudo, com exceção do diquat, os herbicidas foram eficientes no controle das plantas de B. subquadripara, porém todos eles permitiram a rebrota delas.Palavras-chave: anatomia foliar, planta aquática, planta daninha, controle químico.ABSTRACT -The aim of this work was to evaluate the control efficacy of diquat, glyphosate, and imazapyr and the anatomic leaf blade changes caused by these herbicides in B. subquadripara. The plants were grown in reservoirs under field conditions, and, after reaching the full vegetative development stage, were sprayed with solutions of diquat at 400 g ha -1 , glyphosate at 4,320 g ha -1 combined with Aterbane at 0.5% v v -1 , and imazapyr at 750 g ha -1 . A control without herbicide was used. Control evaluations were carried out, followed by evaluation of the anatomic quantitative characteristics of the central vein and intervein regions of the leaf blade, as well as of the stem region: adaxial and abaxial epidermis %, endoderm %, vascular bundle %, aerenchyma lacunas %, parenchyma and leaf thickness %, epidermal stem %, and vascular cambium and stem diameter %. The herbicides diquat and imazapyr promoted the largest number of changes in the quantitative anatomic characters of the midrib and intervein regions of the leaf and stem regions of the plants. However, with the exception of diquat, the herbicides were effective in controlling the B. subquadripara plants. All the herbicides allowed plant re-growth.

Herbicides for Rooted Aquatic Macrophytes

“…In the evaluations at 30, 45, and 60 DAA, the control of B. subquadripara reached 100% at all tested doses, except for the lowest dose (240 g ha -1 ), which was ineffective (Table 1). According to Costa et al (2012), glyphosate was also effective, with 98.8% control of B. subquadripara at a dose of 4,320 g ha -1 + 0.5% Aterbane ® BR at 63 DAA. Cruz et al (2015) also obtained a 100% control for B. subquadripara with a glyphosate dose of 3,360 g ha -1 + 0.5% v/v Aterbane ® BR at 30 DAA, as observed.…”

“…Although visually the control of B. subquadripara and M. aquaticum provided by the herbicide diquat was unsatisfactory (Table 3), Figure 2 shows that diquat doses reduced dry matter accumulation in their plants. According to Costa et al (2012), the occurrence of resprouts in B. subquadripara showed the importance of constant monitoring in the applied areas in order to evaluate the need for reapplication and avoid reinfestation. Because of plant resprouts, over time there would be a recomposition of accumulated dry matter, which would require new applications.…”