The influence of NH4+‐N vs. NO3‐n nutrition on root reductant release by fe‐stressed sorghum1

Abstract
The effect of NH4 + ‐N on root reduction capacity developed during Fe stress was investigated in plants grown in a CaCO3 buffered nutrient solution. After a 3‐day period of Fe stress, reduction capacity was not increased by the presence of NH4 + ‐N in the growth medium or in the extracting solution. Since reductant degradation over time was pH dependent, experiments measuring root reductant release into nutrient solution would be confounded by treatments with different solution pH values. In an unbuffered nutrient solution a differential NH4 + uptake due to the cultivar would affect solution pH and interfere with a reliable interpretation of reductant measurements.