Abstract:

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.

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.

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.

Key words: climate change, filial, isotope, parent, plasticity