Author : Ly Tung

Summary : Experiments in tomato were conducted : (1) to optimize the conditions for the in vivo determination of endogenous nitrate reductase activity (NRA, EC 1.6.6.1) and enhanced NRA (enhanced by nitrate) and at the same time to explore the possibility of using the ratio of enhanced NRA to endogenous NRA as a new approach for predicting nitrogen requirement, and (2) to investigate the product-enhancible characteristics of this enzyme. Using optimum conditions for enhancement, results of several experiments covering wide range of nitrogen fertilization levels showed that the ratio of enhanced NRA to endogenous NRA never exceeded two. Furthermore, preliminary trial revealed that the ratios of enhanced NRA to endogenous NRA did not change with fertilization levels. While more conclusive data are necessary, these observations tend to indicate that this new approach may not be applicable in tomato.