Comparative Study on Activity Changes of Ammonium Uptake, Assimilation and Translocation of the Two, Ambient and Elevated CO₂ Cultured Rice in Nitrogen Status Change.

Abstract

Activity changes of ammonium uptake, assimilation and translocation (UAT) were investigated by growing rice in hydroponic culture ambient (36Pa) or elevated CO₂ (110Pa) using Positron Tracer Emitting Imaging System (PETIS). UAT was measured by ¹³N translocation to the plants from the ¹³NH₄⁺ supplied to the roots was taken up. The UAT per plant weight of 110Pa was higher than 36Pa in nitrogen sufficient culture conditions. 3d-Nitrogen deficiency enhanced the UAT of both 36Pa and 110Pa than the culture conditions. On subsequent experiments, the UAT of 36Pa was down-regulated with following resupply of 2 mM nitrogen for 2h to the 3d-N-starved plants, while the UAT of 110Pa was up-regulated. In case of glutamine treatment instead of nitrogen, the UAT of 36Pa was promoted, but 110Pa UAT was suppressed. Effects of nitrogen status change and elevated CO₂ on ammonium assimilation activity are discussed.