The effect of shading on nitrate metabolism in stalks and blades of celery leaves (Apium graveolens L. var. dulce)

The results of two year studies (2003 − 2004) were presented, concerning the effect of various manners of ‘Tango’ celery shading on NR activity and the contents of NO3 - and NH4 + ions, free amino acids, soluble sugars and dry matter, all of which were determined in the stalks and blades of leaves on three different dates, including the harvest time. Three different shading types were used: shading of leaf stalks only with black film fixed on leaf blade level, whole plant shading and shading by double density planting. Film shading started 16 days before the harvest. In comparison with the control plants, shading, particularly of whole plants, inhibited NR activity in leaf stalks and blades. Nitrate content in celery stalks decreased in the final two weeks of vegetation regardless of the method of