Short-term nitrogen starvation regulates nitrogen metabolism, enhances responsiveness, and improves spinach quality...

Excessive accumulation of nitrate in vegetables can be hazardous to human health, whereas little is known about whether short-term intermittent nitrogen starvation reduce this risk. In this study, we found that nitrogen starvation increased nitrate reductase, nitrite reductase, glutamate synthetase and glutamate dehydrogenase activities. It resulted in a decrease in the activity of glutamine synthetase and nitrate content, while increasing the content of nitrite and ammoniacal nitrogen in spinach. The expression of SoNIA1, SoNiR, SoNRT2.5, SoGS1, SoNADH-GOGAT and SoGDH3 was decrease, while root activity and sugar content were increased, however, there were no significant changes in yield, total nitrogen and protein content in spinach. Additionally, malondialdehyde content increased, while hydrogen peroxide and superoxide anion content decreased under nitrogen starvation compared with the control. In conclusion, a short-term nitrogen starvation can not only modulate the sensitivity of nitrogen metabolism, but also improve the quality of spinach well not reducing the yield.