Ação protetora do óxido nítrico em plantas de soja (Glycine max L. Merril) submetidas ao lactofen
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Data
2007-08-10
Autores
Ferreira, Leonardo Cesar [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O lactofen é um herbicida do grupo dos difenil-éteres utilizado na cultura da soja para o controle de plantas daninhas de folhas largas e possui como mecanismo de ação a inibição da enzima protoporfirinogênio oxidase (Protox), que catalisa a etapa de oxidação do protoporfirinogênio-IX a protoporfirina-IX (proto-IX) na via de biossíntese das clorofilas e citocromos. A inibição é seguida de um acúmulo de proto- IX, que leva à formação de espécies reativas do metabolismo do oxigênio (ERMO), peroxidação de lipídios das membranas e diminuição dos teores de pigmentos fotossintéticos, caracterizando-se assim o estresse oxidativo. Como conseqüência, podem ocorrer manchas, enrugamento e queima das folhas, levando à paralisação temporária do crescimento da cultura. Em contrapartida, o óxido nítrico (NO) é uma molécula capaz de eliminar diretamente as ERMO e assim finalizar reações propagadas em cadeia, podendo atuar como um antioxidante. Desta forma, o presente estudo teve como objetivo avaliar se o pré-tratamento de plantas de soja com solução de nitroprussiato de sódio (SNP), substância doadora de NO, promove proteção contra o estresse oxidativo gerado pelo lactofen. Assim, plantas de soja no estádio fenológico V3, após pré-tratamento com as diferentes doses de SNP (0, 50, 100 e 200 μmol.L-1) por dois dias consecutivos, foram pulverizadas com lactofen na dose recomendada para esta cultura, equivalente a 0,7 L.ha-1. Às 24, 48, 72, 96 e 120 h após a aplicação de lactofen (HAAL), folíolos foram coletados para a quantificação dos teores de lipoperóxidos, clorofilas totais e suas frações a e b e carotenóides totais, bem como para a determinação da atividade das enzimas antioxidantes glutationa S-transferase (GST), superóxido dismutase (SOD), catalase (CAT) e peroxidase (POD). Além disso,...
Lactofen is a diphenylether herbicide applied in soybean fields to control broadleaf weeds whose mechanism of action is the inhibition of protoporphyrinogen oxidase (Protox) enzyme, which catalyses oxidation of protoporphyrinogen-IX to protoporphyrin-IX (proto-IX) in the chlorophyll and cytochrome biosynthesis pathway. This inhibition is followed by accumulation of proto- IX, which leads to generation of reactive oxygen species (ROS), lipid peroxidation of membranes and decrease of photosynthetic pigment levels, which characterizes oxidative stress. Consequently, spots, wrinkles and leaf burn can occur, which results in transitory cessation of crop growth. However, nitric oxide (NO) is a molecule able to scavenge ROS directly and to end chain reactions, acting as an antioxidant. Thus, the present research aimed to evaluate if the pre-treatment of soybean plants with sodium nitroprusside (SNP) solution, a NO donor substance, promotes protection against oxidative stress generated by lactofen. Thus, soybean plants at V3 phenologic stage were pre-treated with different SNP levels (0, 50, 100 and 200 μmol.L-1) for two consecutive days and on the third day were sprayed with lactofen at recommended rate for this crop, equivalent to 0.7 L.ha-1. At 24, 48, 72, 96 and 120 h after application of lactofen (HAAL), leaflets were collected in order to quantify the levels of lipoperoxides, total chlorophylls and their a and b fractions, total carotenoids, as well as the activity assay of glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) antioxidant enzymes. In addition, at two, four and seven days after application of lactofen (DAAL), visual injury evaluations were performed, and at 7 and 14 DAAL, the plants were evaluated for height, root length and leaflets number count. Afterwards, the plants were separated into leaf blades,...(Complete abstract click electronic access below)
Lactofen is a diphenylether herbicide applied in soybean fields to control broadleaf weeds whose mechanism of action is the inhibition of protoporphyrinogen oxidase (Protox) enzyme, which catalyses oxidation of protoporphyrinogen-IX to protoporphyrin-IX (proto-IX) in the chlorophyll and cytochrome biosynthesis pathway. This inhibition is followed by accumulation of proto- IX, which leads to generation of reactive oxygen species (ROS), lipid peroxidation of membranes and decrease of photosynthetic pigment levels, which characterizes oxidative stress. Consequently, spots, wrinkles and leaf burn can occur, which results in transitory cessation of crop growth. However, nitric oxide (NO) is a molecule able to scavenge ROS directly and to end chain reactions, acting as an antioxidant. Thus, the present research aimed to evaluate if the pre-treatment of soybean plants with sodium nitroprusside (SNP) solution, a NO donor substance, promotes protection against oxidative stress generated by lactofen. Thus, soybean plants at V3 phenologic stage were pre-treated with different SNP levels (0, 50, 100 and 200 μmol.L-1) for two consecutive days and on the third day were sprayed with lactofen at recommended rate for this crop, equivalent to 0.7 L.ha-1. At 24, 48, 72, 96 and 120 h after application of lactofen (HAAL), leaflets were collected in order to quantify the levels of lipoperoxides, total chlorophylls and their a and b fractions, total carotenoids, as well as the activity assay of glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) antioxidant enzymes. In addition, at two, four and seven days after application of lactofen (DAAL), visual injury evaluations were performed, and at 7 and 14 DAAL, the plants were evaluated for height, root length and leaflets number count. Afterwards, the plants were separated into leaf blades,...(Complete abstract click electronic access below)
Descrição
Palavras-chave
Plantas - Efeito dos herbicidas, Oxido nitrico, Fisiologia vegetal, Enzimas antioxidantes, Antioxidant enzymes
Como citar
FERREIRA, Leonardo Cesar. Ação protetora do óxido nítrico em plantas de soja (Glycine max L. Merril) submetidas ao lactofen. 2007. 155 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Biociências de Botucatu, 2007.