ELECTROLYTE LEAKAGE AND THE PROTECTIVE EFFECT OF NITRIC OXIDE ON LEAVES OF FLOODED RICE EXPOSED TO HERBICIDES

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 mu M 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% (MPC 50). Subsequently, leaf segments were pre-treated with 0, 200 and 2,000 mu M 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 CMP 50, and the protective effect was reassessed in the presence of nitric oxide scavenger, cPTIO. The MPC 50 was caused by exposure to 188.9, 273.4, 410.2 + 205.1 and 917.0 mu M of Oxadiazon, Oxyfluorfen, Paraquat + Diuron and Clomazone. Pretreatment with 200 mu M of SNP reduced electrolyte leakage in leaf segments exposed to 2 and 4 times the MPC 50 to oxadiazon and paraquat + diuron, while 2,000 mu M reduced the damage caused by oxyfluorfen, at the same concentrations. Also, 200 and 2,000 mu M of SNP were efficient for clomazone, and the protection was confirmed by cPTIO in all cases.