LAUSR

The influence of six greenhouse cover types on the development of the vegetative phase of cultivated tomato plants (Lycopersicon esculentum Mill.) was analyzed. The cover films were manufactured by extrusion – blow molding. Special emphasis was put on measuring root, stem and leaf length and dry matter content of the plants, the results of which were compared to those obtained from plants sown outdoors. As expected, the cultivated plants exhibited more vigorous growth when compared to that of the plants grown under free exposure. Films additivated with polymers allowing higher percentages of light transmission and haze determined higher greenhouse inner temperatures, which, in turn, promoted biomass production in the plantation. The presence of an infrared blocker in the plastic film formulations prevented the temperature inside the greenhouses from decreasing drastically below the outer temperature overnight. Additives such as the UV absorber SMARTLIGHT RL1000™ and the red pigment IRGALITE BASF® 2BP™, which increase the amount of red light received by the plants, thus modifying the R:RF ratio, were found to affect the morphology of the studied plants. Although the effect of photomorphogenesis is weak, a slight decrease in the length and area of the tomato leaves could be observed when the R:RF ratio was high.