Abstract: The resultsofthe experimentwhich the differentconcentrationsofcalmodulin antagonist—— CPZwere supplied to 1/2 Hoagland cultural solution showed that CPZinhibited the uptake of nitrate and its transformation into organic nitrogen in wheat seedlings, and the root was more sensitive to CPZthan the leaf.This coincided with the variations of nitrate reductase and glutamine synthetase activities in the same organ in wheatseedlings under the treatmentof CPZ.Finally, CPZresulted in the decrease of dry weight of root and upground parts of wheat seedlings.CPZcaused the increase of total calcium content in wheat seedlings.The results indicated thatcalmodulin, as a memberofthe second messengersystem, probably plays an important role in regulation of nitrogen assimilation in plants.