Electrolyte Leakage and the Protective Effect of Nitric Oxide on Leaves of Flooded Rice Exposed to Herbicides

Portuguese. RESUMO O óxido nítrico atua no sistema antioxidante das plantas e pode conter o dano de herbicidas elicitores de estresse oxidativo, que causam a desorganização de membranas e o extravasamento do conteúdo celular. Com o objetivo de avaliar o efeito protetor do óxido nítrico sobre o extravasamento de eletrólitos, segmentos foliares do cultivar de arroz irrigado Puitá INTA CL foram incubados com 0, 5, 50, 500 e 5.000 M dos herbicidas clomazone (360 g i.a. L-1), oxadiazon (250 g i.a. L-1), oxyfluorfen (240 g i.a. L-1) e com a mistura formulada de paraquat (200 g i.a. L-1) + diuron (100 g i.a. L-1), para obtenção da condutividade máxima potencial de 50% (CMP50). Posteriormente, segmentos foliares foram pré-tratados com 0, 200 e 2.000 M de nitroprussiato de sódio (SNP) por quatro horas e, após, incubados por 48 horas, com 0, 0,5, 1, 2 e 4 vezes a concentração dos herbicidas que causou a CMP50, sendo o efeito protetor reavaliado na presença do sequestrador de óxido nítrico, cPTIO. A CMP50 foi causada pela exposição a 188,9; 273,4; 410,2 + 205,1; e 917,0 M de oxadiazon, oxyfluorfen, paraquat + diuron e clomazone. O pré-tratamento com 200 M de SNP reduziu o extravasamento de eletrólitos nos segmentos foliares expostos a duas e quatro vezes a CMP50 de oxadiazon e paraquat + diuron, enquanto 2,000 M reduziram o dano causado pelo oxyfluorfen, nas mesmas concentrações, assim como 200 e 2,000 M de SNP foram eficientes para clomazone, sendo a proteção confirmada pelo cPTIO em todos os casos.

English. ABSTRACT The nitric oxide acts on the antioxidant system of plants and can discontinue the damage of herbicides elicitors of oxidative stress that cause the disruption of membranes and leakage of cellular contents. In order to evaluate the protective effect of nitric oxide in electrolytes leakage, leaf segments of the Puita INTA CL rice cultivar were incubated with 0, 5, 50, 500 and 5,000 μM clomazone (360 g a.i. L-1), oxadiazon (250 g a.i. L-1), oxyfluorfen (240 g a.i. L-1) and the formulated mixture of paraquat (200 g a.i. L-1) + diuron (100 g a.i. L-1) to obtain the maximum potential conductivity of 50% (MPC50). Subsequently, leaf segments were pre-treated with 0, 200 and 2,000 μM of sodium nitroprusside (SNP) for four hours and further incubated for 48 hours with 0, 0.5, 1, 2 and 4 times the concentration of the herbicide that caused the CMP50, and the protective effect was reassessed in the presence of nitric oxide scavenger, cPTIO. The MPC50 was caused by exposure to 188.9, 273.4, 410.2 + 205.1 and 917.0 μM of Oxadiazon, Oxyfluorfen, Paraquat + Diuron and Clomazone. Pretreatment with 200 μM of SNP reduced electrolyte leakage in leaf segments exposed to 2 and 4 times the MPC50 to oxadiazon and paraquat + diuron, while 2,000 μM reduced the damage caused by oxyfluorfen, at the same concentrations. Also, 200 and 2,000 μM of SNP were efficient for clomazone, and the protection was confirmed by cPTIO in all cases.