Folia Horticulturae

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The effect of the kind of polyethylene film used for cover of low tunnels and plant shading before harvest on nitrate metabolism in butterhead lettuce

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
**e-mail: rwojciechowska@bratek.ogr.ar.krakow.pl

In 2005–2006 the films of various colours (transparent, white, and black) made of original and recycled material were used in low tunnels and plant shades before harvest of butterhead lettuce ‘Melodion’. Nitrate content, nitrate reductase activity as well as ammonium ions and free amino acid content were estimated in leaves. In the first experiment lettuce was grown in the tunnels since day of planting, then the films were taken off 12-13 days before harvest and in the second one – film shades of proper colour and origin were fixed on the low tunnel structure a week before the harvest. Nitrate metabolism was more significantly modified in the second experiment. In both experiments (tunnels and shades) with the reducing of film permeability for PAR, the decrease of nitrate reductase activity and increase of nitrates in lettuce leaves were shown. This phenomenon was accompanied by the decrease of NH4+ ions and in the case of black film by a higher level of free amino acids. The film colour had a greater effect on nitrate contents and their metabolism than the material of the film.

Wojciechowska R., Siwek P., 2007. The effect of the kind of polyethylene film used for cover of low tunnels and plant shading before harvest on nitrate metabolism in butterhead lettuce. Folia Horticulturae 19/2: 99-107.