Characteristics of NH4+ and NO3− fluxes in tea (Camellia sinensis) roots measured by scanning ion-selective electrode technique

As a vital beverage crop, tea has been extensively planted in tropical and subtropical regions. Nitrogen (N) levels and forms are closely related to tea quality. Based on different N levels and forms, we studied changes in NO 3 − and NH 4 + fluxes in tea roots utilizing scanning ion-selective electrode technique. Our results showed that under both single and mixed N forms, influx rates of NO 3 − were much lower than those of NH 4 + , suggesting a preference for NH 4 + in tea. With the increase in N concentration, the influx rate of NO 3 − increased more than that of NH 4 + . The NH 4 + influx rates in a solution without NO 3 − were much higher than those in a solution with NO 3 − , while the NO 3 − influx rates in a solution without NH 4 + were much lower than those in a solution with NH 4 + . We concluded that (1) tea roots showed a preference for NH 4 + , (2) presence of NO 3 − had a negative effect on NH 4 + influx, and (3) NH 4 + had a positive effect on NO 3 − influx. Our findings not only may help advance hydroponic tea experiments but also may be used to develop efficient fertilization protocols for soil-grown tea in the future.