Nitrate confers rice adaptation to high ammonium by suppressing its uptake but promoting its assimilation.

Dear Editor, Nitrogen(N)is the most important macronutrient driving plant growth and development.For higher plants,inorganic N including nitrate(NO3-)and ammonium(NH4+)are predominant N sources(Hu et al.,2023).Nitrate needs to be firstly reduced into ammonium to implement its assimilation,thus requiring a higher energy consumption than ammonium,making ammonium more cost effective for plants.However,ammonium usually causes severe growth retardation of plants under high concentration,which is known as ammonium toxicity.