The effects of O₃ on visible injury and stomatal conductance for water vapor transfer were determined during the leaf development of sunflower plant (Helianthus annuus L. cv. Russian Mammoth) . The stomatal frequency and conductance were also measured during the leaf development. The foliar necrosis induced by the exposure to O₃ was influenced by the leaf age. With increasing leaf age, the foliar necrosis increased from young to mature leaves, then decreased in senescent leaves. The effect on stomatal conductance was also influenced. The inhibition of stomatal conductance on the pretreatment value basis decreased from young to senescent leaves. The degree of foliar necrosis had no linear relationship to the calculated uptake rate of O₃ suggesting that the agedependent foliar sensitivity to O₃ could not be determined by the amount of O₃ incorporated into leaves but by the detoxicating capacity of absorbed O₃ in the leaf.

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The effects of various amending materials on seed germination in saline environment, and the related mechanism were studied. The seed germination tests were considered as bioassay for treatment efficiency under salinity stress. The tests were carried out in petri dishes, at 25°C in the dark for 5 days. Generally organic materials more efficiently reduced the toxic effects of the salt than inorganic materials did. Of organic materials, farm yard manure of 3-4 months decomposition period, and of inorganic materials, Kanuma soil were the most effective ones. The effective materials deactivated considerable amount of ion (Na) through ion holding mechanism.

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The forcing culture of strawberry‘Nyoho’was carried out in a rockwool culture system using slow releasing fertilizer and the following results were obtained.
Each runner plant was raised in a cubic rockwool pot and top-dressed with 0.5 g of 70-day type of slow releasing fertilizer (Nutricote, N: P₂O₅: K₂O=14: 12: 14) on July 20. The fertilizer was removed on August 4 after cutting out the plant from the runner. In this case, the flowerbud formation initiated on September 8. This result showed that the removal of fertilizer promoted the initiation of flower-bud formation in summer compared to retaining the fertilizer until September 8.
Eight plants raised in rockwool pots were placed on a rockwool bed on September 8 and topdressed with 140 g of 140-day type of slow releasing fertilizer. Water was supplied using irrigation tubes for a few minutes a day.
In this culture system, flower buds of the 1st cluster emerged on October 15 and bloomed on October 26. Fruits were harvested from late November, when plants were grown in an unheated plastic house. The 2nd cluster emerged from December to January. The weight of the harvested fruits from the 1st cluster was 226 g/plant (22 fruits/plant, 2.1 t/10 a) . Harvesting from the 1st cluster was almost finished around late February. Successive harvesting from the other clusters was done and the weight of the total yield was 582 g/plant (54 fruits/plant, 4.7 t/10 a) until the end of May and the adequate yield was obtained.
The rockwool culture system was simplified using the slow releasing fertilizer, and it is expected that soilborne diseases can be prevented and labor efficiency can be increased.

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To collect basic data for a plant factory, effects of photoperiod, light intensity, and CO₂ concentration on the photosynthesis of lettuce were studied throughout the growing period under the conditions of 12-24 h photoperiod, 400-3200 ppm CO₂ concentration, and 137-316μE/m²/s light intensity. The results obtained are: (1) The net photosynthetic rate per plant (NPR) of lettuce decreases with increasing photoperiod when either the CO₂ concentration or the light intensity was increased; (2) At a photoperiod of 24 h, the effect of CO₂-enrichment on the increases in the fresh weight and the dry weight is greater at a lower light intensity of 137 μE/m²/s; (3) At a light intensity of 237 μE/m²/s, both the stomatal resistance and the CO₂ compensation point of lettuce are increased by CO₂-enrichment, the extent of these increases being greater at a photoperiod of 24 h.
Thus, in the case of lettuce, the stomatal resistance and the CO₂ concentration in leaves increase when the integral amount of light energy illuminated per day is increased, which suggest that the CO₂ uptake rate is decreased. It may be concluded that either the continuous illumination of low light intensity or the intermittent illumination of high light intensity is useful for improving the cost effectiveness of cultivating lettuce in plant factory.

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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.

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In the previous studies, photosynthesis generated by the pulsed light was identified with least squares method by taking the mean light flux density as the system input or with spectral analysis based on stochastic theory by sampling the very pulsed light as the system input directly. In this study, we tried to estimate pulse transfer function using the same data as used in the previous study, and transformed the estimated pulse transfer function into state equation, based on which we simulated the effects of the pulsed light by an optimal control algorithm.

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The consumption of three sorts of ions (Ca²⁺, K⁺ and NO₃^-), EC and pH were continuously measured during the growth period of Muskmelons cultivated in NFT.
The diurnal courses in the consumption of Ca²⁺, K⁺ and NO₃^- fluctuated periodically. The negative consumption of ions was observed. This was notable during the night in three sorts of ions. These ion consumption was not correlative to the quantum flux density during the first half of vegetative stage but during the pollinating stage in which the ion consumption became high, it was corresponded to quantum flux density. The consumption of the water caused by the transpiration was in good coincidence with the quantum flux density in every growth stages. The EC decreased until the first half of the developmental stage of fruit but after that stage, it increased. The pH decreased in every growth stages.
The daily patterns in the consumption of Ca²⁺ was small until 15 days after planting but after that time, it increased and reached to the maximum value on 32-37 days after planting. The consumption of K⁺ was also small until 18 days after planting although it increased temporally on 6 days. Then, it increased rapidly and attended to the maximum value on 28-37 days after planting. The consumption of NO₃^- increased from 6 days after planting but decreased temporally on 16-17 and 21-25 days. Then, it increased rapidly and attended to the maximum value on 28-30 days after planting. The consumption of the water increased with the growth.

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These studies were carried out for the development of non-invasive and continuous measurements of the variations of water content in the living plant tissue. The purposes are to measure plant physiological informations, to apply the methods to the estimation of physiological effects of water to the plant growth in agriculture and to analyze the effects of air pollutants to the plants.
The following measurements were developed as the results of these studies.
(1) Measurement of variations of stem diameter
(2) Measurement of variations electrostatic capacity of plant stem
(3) Measurement of variations of leaf thickness
The feasibility studies were done mainly in the growth chamber and the greenhouse, and these measurements were found useful. Especially, the measurement of stem diameter variation was useful even in the field.

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