ISHS Acta Horticulturae 260: International Symposium on Growth and Yield Control in Vegetable Production
MORE INTENSIVE PRODUCTION OF LETTUCE UNDER ARTIFICIALLY CONTROLLED CONDITIONS |
| Author: | T. ITO |
| Abstract:
Relative efficiency of 3 light energy sources for growing lettuce plants was examined under controlled environments. The highest fresh and dry weights were obtained under the high pressure sodium lamps (HPS), followed by metal halide lamps (MH) and fluorescent lamps (FL) when compared on the basis of equal incident photosynthetic photon flux (PPF). Higher blue photon flux density increased lettuce quality in terms of dry weight ratio and chlorophyll concentration in the leaf. The highest dry weight and photosynthetic rate were obtained in the plants grown underp HPS enriched with blue photon flux. Optimal PPFD was found to be 280 μ E.m-2. sec-1 in case of 14hrs-photoperiod. In order to reduce the electric charge, flicker-type lamp (mean wave height 60% of full light) was tested at 2 PPFD. Flicker lamp reduced dry matter production by 81%, the amount being almost equivalent to the decrease in photosynthetic rates. Temperature between 16 to 18 °C during dark period were considered to be preferable. Chlorophyll content in the leaf decreased considerably with increasing dark temperature. CO2 concentration at 600 ppm gave the highest growth rate and quality under HPS. Further increase in CO2 concentrations resulted in a slight reduction of fresh weight, although showing higher dry weight ratio and higher chlorophyll content. | |
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