Interchangeable cross-tolerance induced by waterlogging and herbicides in soybean plants

Plants under suboptimal environmental conditions often present reduced crop yields due to effects on vital plant processes. On the other hand, pre-exposure to mildly stressful situations may prepare the plants to stand subsequent challenges. Waterlogging in lowland areas and herbicide injury are frequent stressful situations to which soybeans are exposed. The objectives of this study were to verify the potential effect of herbicide sub-doses on the reduction of oxidative stress caused by waterlogging in the soybean crop and, on the other hand, to verify the inverse situation (i.e., if a pre-exposure to waterlogging could induce some effect on subsequent herbicide injury). Our results indicated that plants early exposed to sub-dose of oxyfluorfen (5.6 g a.i ha(-1)) exhibited a greater capacity to cope with the soil waterlogging, mainly due to the higher superoxide dismutase activity and lower oxidative damage. While the plants pretreated with the herbicide paraquat (3.2 g a.i ha(-1)) did not present significant differences. Moreover, the damage caused by the herbicides was reduced in soybean plants pre-exposed to soil flooding, reducing oxidative damage. These results suggesting the existence of a cross-tolerance between herbicides and soil waterlogging.