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 NO3- and NH4+ fluxes in tea roots utilizing scanning ion-selective electrode technique. Our results showed that under both single and mixed N forms, influx rates of NO3- were much lower than those of NH4+, suggesting a preference for NH4+ in tea. With the increase in N concentration, the influx rate of NO3- increased more than that of NH4+. The NH4+ influx rates in a solution without NO3- were much higher than those in a solution with NO3-, while the NO3- influx rates in a solution without NH4+ were much lower than those in a solution with NH4+. We concluded that (1) tea roots showed a preference for NH4+, (2) presence of NO3- had a negative effect on NH4+ influx, and (3) NH4+ had a positive effect on NO3- 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.