Influence of UV blocking material on the growth, development and production of hydroponically grown tomato (Lycopersicum esculentum Mill.)

A new technique used in greenhouses for insect and fungi disease control is the use of UV-absorbing films. The benefits have already been proven, but the effect on the growth and development of tomato plants needs further investigations. The experiments were performed in three similar experimental plastic covered greenhouses, N-S oriented, located at the University of Thessaly near Volos, during spring and summer period of 2002. A common greenhouse cover film with a 5 percent transmission to UV radiation covered one of the three greenhouses (GH1). UV-absorbing films of 3 percent and 0 percent transmission to UV radiation respectively, covered the other two greenhouses (GH2 and GH3, respectively). The plastic films were constructed by PLASTIKA KRHTHS AEBE (Greek Company). Measurements concerning growth, development and fruit production and quality of the plants in the three greenhouses were conducted in addition to environmental measurements. The measurements concerned total radiation and temperatures outside and inside the three greenhouses. The agronomical measurements were in reference to dry matter production and partitioning, plant height, leaf area index, fruit production and quality e.g. pH of the fruits in addition to their SSC, firmness, appearance and weight. The plants in the three greenhouses showed similar behaviour mainly in nodes appearance, dry matter partitioning, and production per truss and fruit quality. As for the total production, leaf area index and leaf dimensions, the behaviour of the plants was not the same but was due to different greenhouse microclimate. The main difference was in the plants height. It seems that the lack of UV enhanced the intemodes height since (at the last measurement) the internodes of the plants in GH3 were 4 percent and 6 percent higher than the ones in GH2 and in GH1 respectively.