>187 The pulse family plant has obtained nitrogen nutrition required for growth from the nitrogen fixation by fertilization of combination state nitrogen, and symbiosis with root nodule bacteria. It is known that combination state nitrogen will check nitrogen fixation, and the nitric acid reduction enzyme (NR) of the vegetable origin in a root nodule may be participating in this prevention mechanism. Nitric acid prevention of nitrogen fixed ability and change of the nitric acid reduction enzyme activity of each organ became clear last year using Lotus japonicus (henceforth Lotus) of a model pulse family plant. According to it, it is a Lotus root nodule site. Unguided type nitric acid reduction enzyme activity was looked at by soll like other pulse family root nodules.