Short-term nitrate supply decreases fermentation and oxidative stress caused by waterlogging in soybean plants

Waterlogging is one of the main causes of agricultural losses around the world, and nitrate nutrition has been demonstrated to mitigate the negative effects of waterlogging in plants. Here we evaluate the effect of short- and long-term nitrate fertilization in waterlogged nodulated soybean plants and comprehensively examine the mechanisms underpinning nitrate fertilization and soybean tolerance against hypoxia. Waterlogging increased fermentation and oxidative stress and decreased ATP levels in the roots of soybean. Waterlogged plants that received nitrate nutrition (short- or long-term) increased the levels of nitric oxide (NO) and partially restored ATP levels. Also, nitrate nutrition reduced the activity of fermentative and antioxidant enzymes as well as the fermentation substrates and reactive oxygen species (ROS) in waterlogged plants. Few metabolic differences resulted from short- and long-term fertilization, and these differences were not sufficient to impair waterlogging tolerance in soybean plants. By infiltrating roots from waterlogged plants with cPTIO (an NO scavenger), we show that enhanced nitrate nutrition-induced accumulation of NO in waterlogged plants proved to be a key factor for soybean tolerance against waterlogging. Increased ATP accumulation and decreased levels of ROS and toxic products derived from fermentation reactions are suggested as crucial mechanisms underpinning the tolerance of soybean plants under waterlogged conditions.