Use of UV radiation for control of height and conditioning of tomato transplants (Lycopersicon esculentum Mill.)

Treatments in greenhouse of plug transplants of tomato (Lycopersicon esculentum Mill. CV. Marmande) with supplemental UV radiation from fluorescent lamps were performed to control plant height and to condition them to outdoor conditions. Our investigation examined how tomato transplants responded to varying doses of UV radiation at different time of year (winter-spring). UV treatments, depending on the dose, significantly lowered plant height (up to 47%), leaf area (up to 65%) and shoot dry weight (up to 56%). The effects of UV treatments depended on both the daily applied dose and the environmental conditions. UV treatments were effective on tomato plants in winter, i.e., in the presence of low PAR, as well as in spring, i.e., in presence of high PAR. The main effect of the presence of high PAR was the enhancement of the threshold dose of UV energy required for induction of evident morphological damage to tomato plants. Blooming time and early production was similar in untreated and W-treated plants, irrespective of the presence of the severe reduction of growth produced by UV radiation. (C) 1997 Elsevier Science B.V.