The closed transplant production system is defined as a transplant production system covered with opaque and insulated walls, where the energy and mass transfer between inside and outside the system is controlled and/or restricted, and using artificial lights. CO2 utilization efficiency of a closed transplant production system, CUE, was defined as the ratio of the amount of CO2 fixed by plants to that supplied into the system. Water utilization efficiency of the system, WUE, was defined in the same way as CUE. Tomato seeds were sown on plug trays and grown for 20 days in the system. CUE and WUE increased with increasing leaf area index (LAI) and decreasing the number of air exchanges. Maximum CUE (0.93) and WUE (0.95) during the present study were obtained at maximal LAI of 1.2 and minimal number of air exchanges of 0.02 h-1. Results suggest that a high LAI and a low number of air exchanges provide high CUE and WUE values.
To establish an environment-friendly hydroponics system, the ion concentration control method for nutrient solution was developed.This demonstrated to be superior to the EC control method in respect to reduction of effluent and increase of yield. In this study, the technique for keeping a suitable pH value without using acid and/or alkali was examined; plants were cultivated under three concentrations of NH4-N. When the set point concentration of NH4-N was high, the pH value of nutrient solution fell rapidly after compensation of the component. However, when the set point of concentration of NH4-N was 5-8 mg l-1, the pH was rather stable. The pH value becomes stable when the ratio of NO3-N to NH4-N of nitrogen source is around 30 (total N: 120∼240 mg l-1). From the result of the comparative experiment on nutrient solution control methods on cucumber, it was suggested that new ideas on NH4-N supply should take into consideration of the ion concentration control method and that it includes not only set points of NH4-N concentration value but also the ratio of NH4-N to NO3 -N in the ion concentration.
This study evaluated three types of combustion type CO2 fertilization systems: The thermal storage type (excess heat energy is stored and used for heating), the heat waste type (excess heat is discharged outdoors), and the diffusion type (excess heat is discharged indoors). We analyzed the validity, energy-conserving, environmental load-reducing, and cost-reducing characteristics of these types, and reached the following conclusions. 1)The excess heat generated by combustion type CO2 fertilization accounted for several percentages of the daily cumulative solar irradiation during the intermediate period under the standard condition in this study (amount of CO2 fertilization,48 g (CO2) m-2d-1). The thermal storage type is expected to prevent the aggravation of the thermal/humidity environment in the greenhouse and decrease the efficiency of supplied CO2. 2)Using the thermal storage type,a maximal energy conservation of 8% and a reduction in CO2 discharge can be expected in large greenhouses (annual energy consumption in the entire greenhouse, about 3 GWh) under the standard conditions of this study (summer/intermediate period ratio, 0.33; thermal storage/discharge efficiency, 0.8). 3)The unit cost of CO2 fertilization using this thermal storage type was about 25 yen kg-1 (during depreciation) and about 12 yen kg-1 (after depreciation) under the standard conditions of this study (summer/intermediate period ratio, 0.33; price of unit quantity of heat, 5.5 yen kWh-1; thermal storage/discharge efficiency, 0.8). To reduce the unit cost of CO2fertilization, improvement in thermal storage/discharge efficiency, a decrease in fuel cost, and an increase in the number of days in operation during the intermediate period are necessary.
Horseradish (Armoracia rusticana) hairy roots were established by transformation with the Ri plasmid T-DNA in Agrobacterium rhizogenes 15834. To elucidate the effects of sugar and osmotic pressure on the differentiation of adventitious shoots in horseradish hairy roots, the hairy-root clone AR450 was cultured in phytohormone-free LS medium containing sucrose, glucose,and fructose under light conditions. Adventitious shoots were formed in the presence of 1.5% (W/V) glucose or 1.5% (W/V) fructose as well as in the presence of 3% (W/V) sucrose. High osmotic pressure inhibited the formation of adventitious shoots in horseradish hairy roots. Adventitious shoots were also formed effectively in liquid LS medium without phytohormones under light conditions.
Regeneration procedures for Pharbitis nil Choisy cv. Violet, a recalcitrant species for plant regeneration in vitro, were established using immature zygotic embryos as starting materials. Embryogenic calli were formed in LS (5% sucrose) medium containing 1×10-5 M of 4-fluorophenoxyacetic acid (Emc medium) under light conditions,and transferred to LS (5% sucrose) medium containing 1.5×10-5 M of abscisic acid and 3×10-6 M of gibberellic acid (Eb medium) to form adventitious embryos. Plantlets were regenerated in LS (3% sucrose) medium (Plt medium) after 8 to 9 weeks of culture. The regenerated plants were induced to flower by a single short-day treatment in vitro.