Soil waterlogging associated with iron excess potentiates physiological damage to soybean leaves

Abstract

Many plants are exposed to soil waterlogging, including soybean plants. Soil waterlogging exponentially increases the availability of iron (Fe) and causes O2 depletion, which may result in excessive uptake of Fe and shortage of O2 to the roots and also nodules in leguminous plants, resulting in overproduction of reactive oxygen species and lipid peroxidation. The present study aimed to evaluate physiological damage to soybean leaves at the second trifoliate (V2) stage when exposed to non-waterlogged and waterlogged soils and combined with one moderate and two toxic levels of Fe. Soybean plants were vulnerable to soil waterlogging at all Fe levels tested, presenting the highest values of malonaldehyde, hydrogen peroxide, and Fe accumulation in the shoot, which resulted in accentuated damage to gas exchange and chlorophyll content, consequently leading to lower shoot dry weight. In contrast, soybean plants cultivated under optimal water availability showed less damage caused by excess Fe, mainly at 125 mg dm-3 Fe, since the traits of net photosynthetic rate, water use efficiency, instantaneous carboxylation efficiency, malonaldehyde, and shoot dry weight were not affected.