Nitrate induction and physiological responses of two maize lines differing in nitrogen use efficiency: effects on N availability, microbial diversity and enzyme activity in the rhizosphere

The rate of nitrate (NO3 (-)) uptake and changes in rhizosphere properties were studied growing seedlings of two maize inbred lines differing in nitrogen use efficiency (NUE) in rhizoboxes. Changes in NO3 (-) uptake rates occurred in response to anion addition (induction) in seedlings grown both in hydroponic culture and in soil in rhizoboxes. The characterization of root exudate composition showed a line-specific metabolite profile, which was also affected by NO3 (-) availability. The induction affected respiration, nitrification, ammonification and enzyme activities of the rhizosphere. Furthermore, the composition of rhizosphere bacterial communities of the two maize lines differed suggesting the selective capacity of plants. Overall, results showed a strong and fast modification of rhizospheric soil properties in response to physiological changes in plants caused by fluctuating NO3 (-) availability.