Because of the link between chlorophyll content and nitrogen content in leaves, chlorophyll fluorometers can be used to detect nitrogen deficiency in plants, by several methods.
Based on several years of research and experimentation, polyphenols can be the indicators of nitrogen status of a plant. For instance, when a plant is under optimal conditions, it favours its primary metabolism and synthesises the proteins (nitrogen molecules) containing chlorophyll, and few flavonols (carbon-based secondary compounds). On the other hand, in case of lack of nitrogen, we will observe an increased production of flavonols by the plant.
The NBI (Nitrogen Balance Index) by Force-A, allows the assessment of nitrogen conditions of a culture by calculating the ratio between Chlorophyll and Flavonols (related to Nitrogen/Carbon allocation) .