Expression of Nitrate and Nitrite Reductase Activities under Various Forms of Nitrogen Nutrition in Phaseolus vulgaris L.

Abstract
The main objectives of this work were to study the effect of different N sources on plant growth, N accumulation, and on the expression of nitrate reductase activity in Phaseolus vulgaris L. leaves. Plants were grown under greenhouse conditions (15 to 25 kilolux; 16/8 hour day/night cycles) in plastic pots filled with perlite: vermiculite (1:1) and watered daily with a minus N solution (N2 plants) or supplemented with either KNO3, (NH4)2SO4, or urea as combined N sources.