Abstract
Plants use nitrate, ammonium, and organic nitrogen in the soil as nitrogen sources. Since the elevated CO2 environment predicted for the near future will reduce nitrate utilization by C3 species, ammonium is attracting great interest. However, abundant ammonium nutrition impairs growth, i.e., ammonium toxicity, the primary cause of which remains to be determined. Here, we show that ammonium assimilation by GLUTAMINE SYNTHETASE 2 (GLN2) localized in the plastid rather than ammonium accumulation is a primary cause for toxicity, which challenges the textbook knowledge. With exposure to toxic levels of ammonium, the shoot GLN2 reaction produced an abundance of protons within cells, thereby elevating shoot acidity and stimulating expression of acidic stress-responsive genes. Application of an alkaline ammonia solution to the ammonium medium efficiently alleviated the ammonium toxicity with a concomitant reduction in shoot acidity. Consequently, we conclude that a primary cause of ammonium toxicity is acidic stress.
Highlights
IntroductionAmmonium, and organic nitrogen in the soil as nitrogen sources. Since the elevated CO2 environment predicted for the near future will reduce nitrate utilization by C3 species, ammonium is attracting great interest
Plants use nitrate, ammonium, and organic nitrogen in the soil as nitrogen sources
Discussion ammonium is believed to be a toxic compound for plant growth, our results demonstrate that ammonium assimilation by shoot GLUTAMINE SYNTHETASE 2 (GLN2) rather than ammonium accumulation is a major cause of ammonium toxicity
Summary
Ammonium, and organic nitrogen in the soil as nitrogen sources. Since the elevated CO2 environment predicted for the near future will reduce nitrate utilization by C3 species, ammonium is attracting great interest. Increasing ammonium use by crops is an important goal for agriculture as CO2 levels rise in the world; millimolar concentrations of ammonium as the sole N source causes growth suppression and chlorosis in plants, compared with nitrate or lower concentrations of ammonium[3,4,5]. This phenomenon is widely known as ammonium toxicity, but the primary cause of impaired growth remains to be identified; in the present study, ammonium toxicity is defined as shoot growth suppression with toxic levels of ammonium as the sole N source compared with nitrate. A genetic screen focusing on severely chlorotic Arabidopsis leaves identified
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have