Effect of photoselective plastics on the quality of lettuce

The aim of the experiments was to assess the effect of far-red filter on the quality of lettuce plants. Half of the experiments with lettuce were carried out in the springtime on the field near Visusti in 2000 and 2001. Plants were grown in open land with and without far-red filter. The other half of the experiments with lettuce were carried out in the greenhouses of the University of Tartu, Institute of Plant Physiology in 2000 and 2001. The colour of plants grown under far-red filter was beautiful light green compared to plants grown in control, which were yellowish, darker green. Under far-red filter plants tasted less bitter compared to plants in the control. Scattered radiation penetrated deeper inside of lettuce than direct beam. Therefore spectral filter affected also leaf orientation. Lettuce leaf position became more upright in control plants compared to plants grown under a far-red absorbing film. The incidence of tipburned leaves decreased under far-red filter. The yield was not significantly different. Calcium content was significantly higher under far-red filter. Plants grown under far-red filter contained less dry matter and chlorophyll.