Unraveling nitrate-mediated mechanisms in response to ammonium toxicity in plants

Intensive use of nitrate in agriculture has resulted in serious environmental and health problems; however, using ammonium as an exclusive, alternative nitrogen source can have deleterious effects on plant growth. Even at very low concentrations, nitrate counteracts ammonium toxicity in plants, although the molecular nature of this phenomenon remains unclear. In this thesis, we explore the genetic and metabolic mechanisms involved in nitrate-driven ammonium detoxification in species of agricultural interest, such as spinach (Spinacia oleracea L.) and pea (Pisum sativum L.), as well as in the model plant Arabidopsis. The evidence indicates that nitrate alleviates processes that are compromised in ammonium toxicity syndrome, including ammonium uptake- and assimilation-mediated pH stress, potassium homeostasis disturbance, hormonal imbalance, and the strong demand for carbon supply. A better understanding of the mechanisms underlying these beneficial effects will help to modernise agriculture through the efficient design of fertilisers for more sustainable and efficient use of nitrogen.