Evaluating nitrogen uptake: Methods and applications for plant research

Nitrogen is an essential nutrient for the growth and development of plants, aiding many physiological and biological functions. Due to the high demand for the nutrient, it is common for agricultural production systems to fertilize crop fields with large quantities of nitrogen. However, excessive fertilization can be harmful economically and environmentally. Understanding the mechanism by which plants take up nitrogen from their environment is critical to optimize plant growth and agricultural productions. Over the past several decades, researchers have used a variety of methods to quantify nitrogen uptake, including using nitrogen isotopes, measuring uptake through depletion of a solution over time, using compartmented chambers or agarose blocks to target specific root regions, and more recent small-scale approaches such as nanoscale secondary ion mass spectrometry (nanoSIMS), microdialysis, and biomarkers. Several of these studies have been conducted in maize due to its high nitrogen demand and significance in global food and feed production; however, these techniques can be applied to any plant system. This review will examine the application of these methods, highlighting their advantages and limitations. By exploring existing methods, we aim to provide insights into advancing nitrogen uptake studies, ultimately supporting sustainable nitrogen management and improving crop production efficiency.