Influ?ncia do glyphosate na anatomia e fisiologia de cultivares de caf? ar?bica

O manejo das plantas daninhas possui grande import?ncia para a manuten??o dos n?veis produtivos da cultura do caf?. O herbicida mais utilizado mundialmente na cultura do caf? ? o glyphosate, por possuir alta efici?ncia e ser mais barato. Ele atua inibindo a enzima 5-enolpiruvilshiquimato, respons?vel pela produ??o de tr?s amino?cidos tirosina, fenilalanina, tryptofano. Influenciando assim a produ??o de metabolitos secund?rios, inclusive os relacionados a forma??o das estruturas anat?micas, metabolitos de defesa e fotoss?ntese. Objetivou-se no presente trabalho avaliar os efeitos da deriva simulada de glyphosate sobre a anatomia e fisiologia de cultivares de caf? arabica. Para isso, fez-se tr?s avalia??es diferenciadas visando avaliar modifica??es primeiramente morfoanat?micas, depois concentra??es de fen?is totais, flavon?ides, cafe?na e por ultimo, floresc?ncia, concentra??es de clorofilas e quantifica??es de est?matos. O experimento foi instalado em esquema fatorial (3 x 5), com tr?s cultivares de caf? MGS Travessia, Oeiras MG 6851 e Catua? IAC 144, e cinco doses de glyphosate (0,0; 57,6; 115,2; 230,4 e 460,8 g ha-1), em delineamento de blocos casualizados, com quatro repeti??es. Trinta dias ap?s a aplica??o, foram coletadas doze folhas rec?m-expandidas do ?ltimo ramo plagiotr?pico do cafeeiro, quatro folhas para as analises anat?micas, quatro para as analises de concentra??es de fen?is, flavonoides, cafe?na e as quatro ultimas para a quantifica??o estom?tica. Nas analises morfoanat?micas observou-se os seguintes resultados: ocorreram sintomas de intoxica??o como estreitamento foliar e clorose nas folhas mais jovens das plantas. Com o aumento da dose de glyphosate, a cultivar Catua? sofreu redu??o na espessura foliar total, enquanto, que para as demais ocorreu incremento nesta caracter?stica. Para as vari?veis epiderme adaxial, epiderme abaxial e par?nquima lacunoso, ocorreu decr?scimo de espessura, contudo ocorreu aumento da espessura do par?nquima lacunoso com aumento das doses de glyphosate. Pode-se concluir que as tr?s cultivares quando submetidas ? deriva de glyphosate sofrem modifica??es morfoanat?micas. Com a redu??o do par?nquima pali??dico ocorre redu??o da taxa fotossint?tica e consequente redu??o do crescimento e produ??o do caf?. Para as analises de concentra??es de fen?is, flavon?ides e cafe?na, observou-se os seguintes resultados: com aumento das doses de glyphosate houve aumento na concentra??o de fen?is totais foliares at? a dose de 115,2 g ha-1 de glyphosate, para as tr?s cultivares, acima dessa dose as concentra??es de fen?is foram reduzidas. No entanto, com aumento das doses de glyphosate a concentra??o de flavon?ides diminuiu at? a dose de 115,2 g ha-1 de glyphosate, para as cultivares Travessia e Oeiras, acima dessa dose a concentra??o de flavon?ides para essas duas cultivares aumentaram. Ocorreu aumento da concentra??o de flavon?ides para a cultivar Catua? quando aplicado a dose de 115,2 g ha-1 de glyphosate, para doses mais altas ocorreu diminui??o da concentra??o de flavon?ides totais. Com aumento das doses de glyphosate, as concentra??es de cafe?na apresentaram comportamento similar entre as cultivares Oeiras e Catua?, ocorrendo diminui??o da concentra??o de cafe?na at? a dose de 115,2 g ha-1 de glyphosate e aumento a concentra??o de cafe?na para doses superiores. Observou-se que houve aumento na concentra??o de cafe?na para cultivar Travessia a partir de 115,2 g ha-1 de glyphosate. De acordo com o teste histoqu?mico todas as tr?s cultivares estudadas apresentaram maiores concentra??o de fen?is no par?nquima pali??dico ap?s a aplica??o da deriva de glyphosate. Conclui-se que, quando submetidas a subdoses de glyphosate, as cultivares analisadas apresentaram modifica??es bioqu?micas para as concentra??es de fen?is totais, flavon?ides totais e cafe?na. Com baixas doses 57,6 e 115,2 g/ ha?? de glyphosate, ocorreu aumento da concentra??o de fen?is totais aumentando assim a capacidade de defesa das cultivares, entretanto com o aumento das doses de glyphosate ocorreu redu??o da concentra??o de fen?is totais. A produ??o de flavon?ides e cafe?na possuem efeitos variados para as doses de glyphosate podendo aumentar e diminuir a concentra??o de forma independente, pois os metabolitos s?o supridos por outras rotas. Nas analises fisiol?gicas, observou-se os seguintes resultados: os valores da vari?vel fluoresc?ncia m?xima (Fm) decresceram de acordo com o aumento das doses de glyphosate, a cultivar Travessia apresentou maior decr?scimo que as demais cultivares. Para efici?ncia fotoqu?mica m?xima (Fv/Fm) ocorreu com o aumento do estresse de acordoo com o aumento das doses aplicadas do glyphosate. As concentra??es de clorofila a, b e total sofreram decr?scimo de acordo com o aumento das doses aplicadas de glyphosate. Para as vari?veis, ?ndice estom?tico e densidade estom?tica ocorreram um decr?scimo de valores de acordo com o aumento da dose aplicada de glyphosate. A cultivar Travessia apresentou maior queda de valor para o ?ndice estom?tico e densidade estom?tica. Conclui-se que as subdoses de glyphosate provocaram danos na fotoss?ntese de forma direta, pois, ocorreu diminui??o das concentra??es das clorofilas e da intensidade da fluoresc?ncia m?xima, promovendo, assim, maior estresse nas cultivares de caf?. A diminui??o do n?mero de est?matos ? mais uma das prov?veis explica??es para a influ?ncia na fotoss?ntese promovida pelo glyphosateConselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2013.Abstract Weed management is greatly important to keep levels of coffee production. Glyphosate is the most used herbicide in the world for being of high efficiency and cheaper. Its action is on the enzyme 5enolpyruvylshikimate that is responsible for producing tyrosin, phenylalanine and tryptophan. It inhibits their production, consequently influencing the production of secondary metabolites, mainly the ones related to anatomical structures, metabolites of defense and photosynthesis. This study was carried out in order to evaluate effects of drift simulation of glyphosate on anatomy and physiology of Arabica coffee cultivars. There were three different stages of evaluations: first morphoanatomical modifications, then concentrations of total phenol, flavonoids and cafeine, and finally fluorescence, chlorophyll concentrations and stomata quantification. The experiment was arranged in a factorial scheme (3 x 5), with three coffee cultivars (MGS Travessia, Oeiras MG 6851 and Catua? IAC 144), at five glyphosate rates (0.0; 57.6; 115.2; 230.4 and 460.8 g ha-1), in a randomized block design, with four replicates. Thirty days after application, twelve recently expanded leaves from the last plagiotropic branches were collected: four for anatomical analysis, four for analysis of concentrations of total phenol, flavonoids and cafeine and four to quantify stomata. Morphoanatomical analysis showed intoxication symptoms such as foliar narrowing and chlorosis on the younger leaves were observed. Increasing glyphosate rate, the cultivar Catua? reduced its total foliar tickness, while to the others it was increased. Adaxial and abaxial epiderms and spongy parenchyma had their thickness decreased, however spongy parenchyma increased at higher rates of glyphosate. It could be concluded that the three cultivars under glyphosate drift shows morphoanatomical modifications. When palisade parenchyma is reduced, consequently photosynthetic rate, growth and coffee production reduce. Analyzing concentrations of total phenol, flavonoids and caffeine, it was observed that phenol concentration increased when glyphosate rates were increased up to 115.2 g ha-1 in all three cultivars, showing reduction at higher rates. For Travessia and Oeiras cultivars, the flavonoid concentration decreased at higher glyphosate rates, starting its increase at rates higher than 115.2 g ha-1. For Catua?, flavonoid concentration increased at 115.2 g ha-1 being reduced with higher rates. Regarding caffeine concentration, it was similar to Oeiras and Catua?. This concentration decreased at 115.2 g ha-1 and got higher at superior rates. The cultivar Travessia showed higher caffeine concentration at rates higher than 115.2 g ha-1. According to the histochemical tests, all the three cultivars present higher phenol concentration on paladise parenchyma after application of glyphosate drift. It can be conclude that, when submitted to subrates of glyphosate, cultivars shows biochemical modifications to all concentrations evaluated. At 57.6 and 115.2 g ha-1 total phenol increased providing a better capacity of defense to cultivars, however, when increasing these rates, total phenol concentration decreased. Flavonoids and caffeine production have varied effects on glyphosate rates. They can increase or decrease independently because metabolites are fulfilled by other ways. Through physiological analysis, it could be observed that values of maximum fluorescence decreased with higher glyphosate rates, and Travessia cultivar presented highest decrease. Chlorophyll concentrations a, b and total decreased according to rates increase, being harder to chlorophyll a. Values of stomatal index and stomatal density decreased when increasing glyphosate rate, being harder to cultivar Travessia. It can be concluded that subrates of glyphosate cause damage on photosynthesis because of the reduction on chlorophyll concentration and fluorescence intensity. Reduction of stomata number is also one of the features that can explain the influence promoted by glyphosate on photosynthesis