Abstract: Photoselective plastic films with thermic properties
are now available so that greenhouses clad with such plastics exhibit
a higher degree of “Greenhouse Effect” with a consequent increase in
night time temperature. In this study, we investigate the potential
benefits of a range of thermic plastic films used as greenhouse cover
materials on the vegetative and reproductive growth and development
of Iceberg lettuce (Lactuca sativa L). Transplants were grown under
thermic films and destructively harvested 4, 5, and 6 weeks after
transplanting. Thermic films can increase night temperatures up to 2
⁰C reducing the wide fluctuation in greenhouse temperature during
winter compared to the standard commercial film and consequently
increased the yield (leaf number, fresh weight, and dry weight) of
lettuce plants. Lettuce plants grown under Clear film respond to cold
stress by the accumulation of secondary products (phenolics, and
flavonoids).