NR is a key enzyme of nitrogen assimilation in plant nitrogen metabolism. It is related with nitrogen absorption in crop, and can affect the yield and quality of crop. Therefore, the NR activity can be considered as one of the indexes of plant nutrition or fertilization, and it can also be used as an important indicator of varieties breeding. Sample Type: Fresh plant Intended Use: This kit can be used for measurement of NR activity fresh plant and other samples. Test Principle: NR can catalyze the reduction of nitrate in plants and form nitrite. The produced nitrite then reacts with chromogenic agent and form red compounds, which can be colorimetric assayed stably at 540nm. Kit Components (see Protocol for final kit quantities): Reagent 1, NR standard stock solution 2mol/L, 1 mLx1 vial Reagent 2, Substrate, 100 mLx1 vial Reagent 3, Chromogenic agent, 100 mLx1 vial Reagent 4, Homogenate medium, 100 mLx1 vial Reagent 5, Revulsive stock solution, 100 mLx1 vial