Ammonium affects cell viability to inhibit root growth in Arabidopsis

Ammonium (NH4+) is an important form of nitrogen nutrient for most plants,yet is also a stressor for many of them.However,the primary events of NH4+ toxicity at the cellular level are still unclear.Here,we showed that NH4+ toxicity can induce the root cell death in a temporal pattern which primarily occurs in the cells of root maturation and elongation zones,and then spreads to the cells in the meristem and root cap.The results from the NH4+-hypersensitive mutant hsn1 further confirmed our findings.Taken together,NH4+ toxicity inhibits primary root growth by inhibiting cell elongation and division and inducing root cell death.