Characteristics of NH 4+ and NO 3- Fluxes in tea (Camellia sinensis) roots measured by scanning ion-selective electrode technique

Abstract

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.