Nitrogenous compounds in 'Homebell' rabbiteye(Vaccinium ashei READE)and 'Jersey' highbush(V. corymbosum L.)blueberry plants were analyzed into 6 fractions, insoluble-N, soluble protein, amino-N, amide, ammonium and nitrate, in relation to N form, N concentration and pH in nutrient solution. In 'Jersey' and 'Homebell' leaves, with raising the pH from 4 to 6, ammonium and amino-N tended to be increased, but soluble protein and insoluble-N were not increased. In 'Jersey' injured by low pH, ammonium was increased, but amide was decreased and soluble protein also tended to be decreased in roots ; amino-N was markedly increased and soluble protein was also increased in shoots ; ammonium and amino-N were increased, but amide and soluble protein were decreased in leaves. In 'Homebell' leaves, amino-N was increased with increasing NH_4-N or NO_3-N supply, while insoluble-N was increased with increasing NH_4-N supply, but that was not increased with increasing NO_3-N supply. In 'Homebell' supplied with NO_3-N compared with NH_4-N, ammonium and amino-N were decreased and amide, soluble protein and insoluble-N also tended to be decreased in roots ; ammonium, amino-N, soluble protein and insoluble-N were decreased in leaves ; amino-N and insoluble-N were decreased in fruits. In 'Homebell' supplied with NH_4NO_3-N compared with NH_4-N, ammonium in leaves was decreased similar to NO_3-N treatment and amino-N in roots, leaves and fruits was increased, while soluble protein and insoluble-N in roots were decreased, but that in leaves and fruits tended to increase. In 'Jersey' injured by high NO_3-N supply, ammonium was increased, but amide was decreased in roots ; soluble protein was decreased in shoots ; ammonium was increased, but amide, amino-N, soluble protein and especially insoluble-N were decreased in leaves. It is elucidated that NO_3-N supply resulted in decreased incorporation of nitrogen into protein of blueberry plants. This might cause the inhibition of blueberry growih when NO_3-N is supplied.
