Fundamental Studies on Factory - Style Plant Production

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A study has been conducted on the fundamental problems which are involved in the factory-style plant production system. In the first year, a growth chamber similar to a plant factory with artificial lights was designed and constructed. As an artificial light source, high pressure sodium lamps were selected because of their highest efficiency to convert electricity to light. Lettuce was used as a test plant and was grown in a hydroponic system which was also developed by us. The levels of EC (Electrical Conductivity of liquid solution) and pH in the liquid solution in three different beds were automatically adjusted by the computer.The effect of light intensity, light period and the ratio of light and dark period on lettuce growth was examined and the effect of the change of EC (electrical conductivity of liquid solution) on the transpiration of lettuce was also analysed using the system we developed.The growth rate and the ratio of dry matter increase were not affected by the change of light period but the shape of leaves was slightly changed. The growth rate increased with the increase of light period and light intensity, on the other hand, the ratio of fresh weight increase was decreased according to the increase of light intensity and light period.It was found that there is a clear relationship among the change of solution concentration, the concentration increase due to the addition of fertilizers, the concentration change due to water supply and that by plant uptake. It was also clear from our experiment that the decrease of EC level and integrated transpiration amount can be correlated.