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Aims Nitrogen (N) in natural environments is typically supplied by a mixture of ammonia (NH4+) and nitrate (NO3-). However, factors that underlie either NH4+ or NO3- preference, and how such preference will change across generations remain unclear. We conducted a series of experiments to answer whether: (i) NH4+:NO3- ratio is the driving factor for plant N preference, and (ii) this preference is consistent across generations.

Methods We conducted both: (i) field observations (as a proxy for parent or P generation) and (ii) greenhouse experiments (the first generation or F1 and the second generation or F2) using corn and soybean grown under different NH4+:NO3- ratios.

Important Findings Both corn and soybean had the physiological plasticity to prefer either NH4+ or NO3- depending on NH4+:NO3- ratios, and this plasticity was consistent across generations. Corn, however, showed a stronger preference towards NO3- while soybean showed a stronger preference towards NH4+. While both plants would try to make use of the most available form of N in their growing medium, plant species, physiological characteristics (e.g. maturity) and plant nutrient status also determined the extent of N uptake. From the evolutionary and productivity perspective, this plasticity is beneficial, allowing plants to effectively acquire available N particularly in a changing climate.