Folia Horticulturae

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

Renata Wojciechowska*, Piotr Siwek**

**Department of Plant Physiology
**Department of Vegetable Crops
**Faculty of Horticulture, Agricultural University in Kraków
**29 Listopada 54, 31-425 Kraków, Poland

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 cultivation. At harvest time, least nitrates were found in leaf stalks of double densed plants. NO3- level was significantly higher in the blades of leaves wholly shaded with black film, in which the lowest content of NH4+ ions was also found. The significant increase of free amino acids in leaf stalks during vegetation occurred regardless of the method of cultivation, with highest amount of this compound presented in plants with shaded stalks as well as wholly shaded plants. Highest soluble sugar content was found in stalks and blades of the celeries cultivated in double density. Dry matter content in both parts of celery leaves was highest in double density treatment and in the control plants.

Wojciechowska R., Siwek P., 2006. The effect of shading on nitrate metabolism in stalks and blades of celery leaves (Apium graveolens L. var. dulce). Folia Horticulturae 18/2: 25-35.