Promotion of Assimilation of Ammonium Ions by Simultaneous Application of Nitrate and Ammonium Ions in Radish Plants

概要

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When radish plants were grown in nutrient solutions that contained ammonium ions (NH_4^+) as the sole source of nitrogen, they grew poorly and accumulated high levels of NH_4^+ in their leaves. However, radish plants cultured in 5 mM NH_4^+ plus 1 mM NO_3^- (a ratio of 5 : 1 in forms of nitrogen; referred to as 5:1 mix-N) grew well and accumulated very low levels of NH_4^+ in their leaves. After radish plants were cultured in solutions that contained NO_3^-, or NH_4^+, or 5:1 mix-N for a week, they were then supplied with the same nitrogen source labeled with ^<15>N for one day. The uptake of ^<15>N from labeled NH_4^+ into total nitrogen was the highest in plants supplied with 5:1 mix-N. These plants converted far fewer labeled NH_4^+ into free NH_4^+ than did NH_4^+-fed plants, but converted many more labeled NH_4^+ into the insoluble fraction than did NH_4^+- or NO_3^--fed plants. The presence of a small amount of nitrate was shown to stimulate the assimilation of ammonium ions and the synthesis of proteins.
日本植物生理学会の論文