Respostas antioxidantes de cultivares de cana-de-açúcar tolerantes à seca e a herbicidas ao déficit hídrico
Carregando...
Arquivos
Data
2019-03-21
Autores
Paula, Ricardo Jardim de
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
A seca é um problema substancial que afeta negativamente parte das áreas de cultivo de cana-de-açúcar, o que limita a produção das lavouras. O déficit hídrico provoca uma redução no crescimento e desenvolvimento das plantas devido à superprodução descontrolada de espécies reativas de oxigênio (ERO). Por outro lado, a aplicação de herbicidas para controle de plantas daninhas é uma estratégia muito usual de manejo nas culturas para manter altos índices de produtividade, mesmo quando as culturas são afetadas por condições adversas, como a seca. Assim, o objetivo deste trabalho foi investigar as diferentes respostas bioquímicas e no crescimento de duas cultivares de cana-de-açúcar, um tolerante à seca (CTC 9002) e outra tolerante a herbicidas (CTC 2), que caracterizem maior tolerância a condição de déficit hídrico associada à aplicação de herbicidas com diferentes mecanismos de ação. Os tratamentos foram dispostos em esquema fatorial triplo 2 x 2 x 3, sendo o fator cultivares CTC2 e CTC9002, fator condição hídrica de 70% ou 35% da capacidade de campo e fator herbicida, ametrina (1750 g i.a. ha-1), sulfentrazone (700 g i.a. ha-1) ou sem aplicação. A peroxidação lipídica, as concentrações de H2O2 e prolina; as atividades antioxidantes das enzimas superóxido dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbato peroxidase (APX, EC 1.11.1.11), glutationa redutase (GR, EC 1.6.4.2); e o acúmulo de massa seca da parte aérea e da raiz foram analisados. A aplicação do herbicida ametrina foi prejudicial às plantas de cana-de-açúcar em decorrência da maior peroxidação lipídica e redução na massa seca das raízes. O aumento da atividade da GR em resposta à aplicação do herbicida sulfentrazone indica que esta enzima pode estar relacionada a um dos mecanismos de tolerância deste grupo de herbicidas. A cultivar CTC2 apresentou aumento da atividade das enzimas APX e SOD quando submetida à aplicação dos herbicidas em relação ao cultivar CTC9002. A CTC2 é tolerante aos herbicidas ametrina e sulfentrazone em relação a CTC9002, principalmente após 7 dias da aplicação. Após 28 dias de déficit hídrico, houve aumento na atividade da enzima APX, o que indica que essa enzima está relacionada ao mecanismo de defesa a essa condição de estresse, contudo, nenhuma das cultivares apresentou diferenças na produção de ERO e no crescimento. A combinação de estresses abióticos envolve uma rede complexa de respostas bioquímicas. Os parâmetros avaliados em ambas cultivares submetidas a aplicação de herbicida sob déficit hídrico não indicam características bioquímicas que pudessem caracterizá-las como tolerantes aos estresses combinados.
Drought is currently a substantial problem worldwide, affecting part of sugarcane grown areas, and it is the main yield-limiting factor of crops. Drought stress provokes a reduction in growth and development due to uncontrolled overproduction of reactive oxygen species (ROS). By the other way, herbicide application to control weeds is a common crop management strategy to maintain high sugarcane yields, even when crops are affected by adverse conditions, such as drought. Thus, the aim of this study was to investigate differences in biochemical and growth responses of two sugarcane genotypes, drought-and herbicide-tolerant, which characterize a greater tolerance to drought stress condition combined to herbicides application with different modes of action. The treatments were arranged in a 2 x 2 x 3 triple factorial scheme, with the cultivar factor CTC2 and CTC9002, a water condition factor of 70% or 35% of field capacity and herbicide factor, ametryn (1750 g a.i ha-1 ), sulfentrazone (700 g a.i ha -1 ) or without application. Lipid peroxidation, H2O2 and proline content; the activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2); and shoot and root dry mass accumulation were analyzed. The ametryn herbicide application was harmful to sugarcane plants due to the higher lipid peroxidation and root dry mass reduction. Increased GR activity in response to sulfentrazone application may indicate that GR enzyme is related to tolerance mechanisms of this herbicide group. The cultivar CTC2 showed an increase in the activity of the APX and SOD enzymes when submitted to herbicide application when compared to CTC9002. Based on these responses, cultivar CTC2 is tolerant to the herbicides ametryn and sulfentrazone in relation of CTC9002, mainly after 7 days of application. Plants which exhibited an increase in APX activity after 28 days of drought stress could indicate that APX enzyme is related to mechanism of tolerance to this stress condition. However, none of the cultivars presented differences in ROS production and growth parameters. The combination of abiotic stresses involves a complex network of biochemical responses. The parameters evaluated in both cultivars submitted to herbicide application under drought stress conditions do not indicate biochemical characteristics that could characterize them as tolerant to the combined stresses.
Drought is currently a substantial problem worldwide, affecting part of sugarcane grown areas, and it is the main yield-limiting factor of crops. Drought stress provokes a reduction in growth and development due to uncontrolled overproduction of reactive oxygen species (ROS). By the other way, herbicide application to control weeds is a common crop management strategy to maintain high sugarcane yields, even when crops are affected by adverse conditions, such as drought. Thus, the aim of this study was to investigate differences in biochemical and growth responses of two sugarcane genotypes, drought-and herbicide-tolerant, which characterize a greater tolerance to drought stress condition combined to herbicides application with different modes of action. The treatments were arranged in a 2 x 2 x 3 triple factorial scheme, with the cultivar factor CTC2 and CTC9002, a water condition factor of 70% or 35% of field capacity and herbicide factor, ametryn (1750 g a.i ha-1 ), sulfentrazone (700 g a.i ha -1 ) or without application. Lipid peroxidation, H2O2 and proline content; the activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2); and shoot and root dry mass accumulation were analyzed. The ametryn herbicide application was harmful to sugarcane plants due to the higher lipid peroxidation and root dry mass reduction. Increased GR activity in response to sulfentrazone application may indicate that GR enzyme is related to tolerance mechanisms of this herbicide group. The cultivar CTC2 showed an increase in the activity of the APX and SOD enzymes when submitted to herbicide application when compared to CTC9002. Based on these responses, cultivar CTC2 is tolerant to the herbicides ametryn and sulfentrazone in relation of CTC9002, mainly after 7 days of application. Plants which exhibited an increase in APX activity after 28 days of drought stress could indicate that APX enzyme is related to mechanism of tolerance to this stress condition. However, none of the cultivars presented differences in ROS production and growth parameters. The combination of abiotic stresses involves a complex network of biochemical responses. The parameters evaluated in both cultivars submitted to herbicide application under drought stress conditions do not indicate biochemical characteristics that could characterize them as tolerant to the combined stresses.
Descrição
Palavras-chave
Saccharum spp., Estresse oxidativo, Enzimas antioxidante, Ametrina, Sulfentrazone