Basic Study on Material Production in Plant Factory (1)

To collect basic data for a plant factory, the net photosynthetic rate per plant, the stomatal resistance, and the CO2 compensation point of turnip which has large sink in root were measured throughout its growing period under the conditions of 12-24 h photoperiod, 400-2100 ppm CO2 concentration, and 137-316 μE/m2/s light intensity. The following results were obtained: (1) The net photosynthetic rate per plant (NPR) of turnip increased remarkably at 24 h photoperiod with increasing either CO2 concentration or light intensity; (2) At 237 μE/m2/s light intensity, the stomatal resistance increased with CO2-enrichment but no appreciable difference was observed between the 12 h and the 24 h photoperiods; (3) At the 24 h photoperiod and 2100 ppm CO2 concentration, the CO2 compensation point of turnip increased slightly; (4) Under the conditions of 24 h photoperiod, 316 μE/m2/s light intensity, and 1100 ppm CO2 concentration, the tuber of turnip grew quite rapidly, which suggests that the tuber plays the role of a sink for the photosynthetic product.Thus, it is considered that the plants with larger sink volumes like turnip can be grown acceleratedly at longer photoperiods, higher light intensities, and higher CO2 concentrations without the reduction in light efficiency.