Nutrients interact: the case of ammonium nutrition and essential mineral cations.

Plant growth and development depends on sufficient nutrient availability in soils. Agricultural soils are generally nitrogen (N) deficient and thus, soils need to be supplemented with fertilizers. Ammonium (NH4  +) is a major inorganic N source. However, at high concentrations ammonium nutrition becomes a stress situation that inhibits plant growth. The cause of ammonium stress or toxicity is multi-factorial but the interaction with other nutrients is among the main determinants of plants sensitivity towards high NH4  + supply. In addition, NH4  + uptake and assimilation provokes the acidification of the cell external medium (apoplast/rhizosphere), which has a clear impact on nutrients availability. This review summarizes current knowledge, at both physiological and molecular level, of ammonium nutrition interaction with essential mineral elements absorbed as cations: macronutrients (K +, Ca 2+, Mg 2+) and micronutrients (Fe 2+/3+, Mn 2+, Cu +/2+, Zn 2+, Ni 2+). We hypothesize that considering these nutritional interactions, and soil pH, when formulating fertilizers may be key in order to boost the use of NH4  +-based fertilizers, which have less environmental impact compared to the nitrate-based ones. In addition, we are convinced that better understanding these interactions will help to identify novel targets with potential to improve crop productivity.