The oxygen regeneration system is one of the most important subsystems for Closed Ecological Life Support Systems (CELSS) . In order to construct an oxygen regeneration system by culturing algae, it is important to know the relationship between the amount of oxygen generated and the culture conditions. From the results of culture experiments with Spirulina platensis, a common blue-green alga for CELSS, it was found that the chlorophyll content of Spirulina varied with the cell density, that is, light conditions in the culture vessel. This suggests that the photosynthetic ability of Spirulina varies with the light conditions. In this study, the net photosynthetic rate of Spirulina was measured, and the effect of light conditions on the photosynthetic rate was investigated. From the results of the measurements, it was clear that the chlorophyll content and relationship between net photosynthetic rate and light intensity varied with the light conditions. Furthermore, when the net photosynthetic rate was represented on a chlorophyll content basis, the relationship between net photosynthetic rate and light intensity was the same relationship for all three cell densities tested.

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Chervils (Anthriscus cerefolium L.), a kind of fresh culinary herb, harvested and packed in drawn polystyrene packages in a commercial operation were stored at 5°C for 27 d under different gas compositions (0.05% CO₂+20% O₂, L ; 0.5% CO₂+ 10% O₂, M; 1 % CO₂+5% O₂, H) at a photosynthetic photon flux density of O (dark, D) or 1 (low light irradiation using an array of red light-emitting diodes, R) μmol m^-2 s^-1, applying (A) or without applying (N) a nutrient agar-gel to the cut ends of their stems. The color difference (ΔEab) value of the leaves of chervils in MRA was kept less than 4 during storage, and was significantly lower than the other treatments including LDN (control : usual low temperature storage) with a ΔE ab of 16 on the last day of storage (day 27) . ΔEab values in LDN, HDN and MRA were less than 3 (stored chervils with ΔEab values less than 3 are considered salable) until day 12, day 18 and day 27, respectively, indicating that storage duration of postharvest chervils stored under controlled atmosphere (CA) and CA combined with low light irradiation and nutrient gel application was prolonged 1.5 times and 2.3 times longer, respectively, than under usual low temperature storage. Subjective visual quality scores showed a similar tendency to that on ΔEab ; the total percentage of scores 3 (salable) and 2 (limit of salability) in MRA and HRA was both 90% while that was 59% in LDN. These results indicate that CA combined with low light irradiation and nutrient gel application was effective for preservation of the visual quality of postharvest chervils during low temperature storage.

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The effect of preharvest fruit temperature on fruit maturity, sugars, and watercore occurrence was investigated in watercore-resistant ‘Tsugaru’ apples (Malus pumila Mill. var. domestica Schneid.) . Watercore appeared at 35/27°C (day/night) in 1990 and at 33 and 38°C in 1991, although a significantly higher watercore rating was observed only at 38°C. Fruit subjected to a 38°C preharvest temperature had higher specific gravity and lower weight than at other lower temperatures in 1991. Fruit maturity judged by ethylene evolution was advanced at 25/17°C more than at other temperatures in 1990 while the influence of fruit temperature on fruit maturity was not obvious in 1991 because all fruit were picked earlier than intended due to the high temperature injury observed at 38°C. Apples at 35/27°C and 38°C showed the lowest starch content in both inner and outer flesh tissue and fruit at 38°C also had the highest soluble solids content (SSC) and total sugars. Fruit at 35/27°C in 1990 and at 33 and 38°C in 1991 had higher glucose and sorbitol and lower sucrose content than at lower temperatures. The results suggest that high fruit temperature above 35°C induces watercore via the rapid starch breakdown and the accumulation of glucose and sorbitol in ‘Tsugaru’ apples.

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We developed a new computerized CCD video light microscopy system for obtaining three-dimensional (3-D) RGB measurements of shape (with color texture) and growth of intact plants under various conditions and over a wide magnification range. We used a modified shape-from-focus algorithm that incorporated a linear regression operator for 3-D reconstruction of images of petunia seedlings, which have a coarse texture. This algorithm was unsuitable for processing images of specimens with glossy texture (e.g., plant cells), but this drawback was mitigated by illuminating the cells in a checked pattern. The algorithm also reduced incorrect range estimates, which are due to defocused areas around the object's edge in original images. Within only a few minutes, the presented system can yield a series of original color images and reconstruct 3-D images incorporating color texture. All operations of our new system are carried out automatically, and the results are displayed by using in-house developed software that allows observation of the reconstructed 3-D image from any direction on the upper side. At angles from 10 to 80° to the objective's face, the surface area can be estimated to within an error of 5%.

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It is necessary that the weed area is discriminated from lawn area if selective spraying is applied to maintain a lawn field. However, both weed and lawn usually have similar green color in summer. In this paper, a color independent method using gray-scale uniformity in image was proposed for detecting the weed area. This method works based on different levels of uniformity for weed and lawn surfaces and could precisely detect only the weed leaves. The analysis results showed that a weed could be detected if its leaves are at least 5 pixels wide in image, while its length is enough to generate a minimum size blob. It was also found that the image had to be acquired at a short camera distance so that the soil among the lawn was visible and the lawn area had less uniformity. After weed leaf detection, a morphological image analysis was performed on a group the adjacent blobs as result of leaf detection. It was observed that the morphological image analysis was useful in locating a representative center-point for grouped blobs in correspondence to main root location of the weeds.

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Soil characteristics of vegetable fields in a semi-arid region at Tianjin City in China were studied. The fields planted with vegetables had a deep plow layer and good physical conditions for plant growth compared with the crop fields. In the vegetable field soils, organic matter, nitrogen and phosphate were accumulated in topsoils with continuous planting. Exchangeable Ca, Mg and Na in vegetable field soils were very high, but K was relatively low, so Ca/K and Mg/K ratios in the soils were extremly high compared with Japanese upland soils: Microflora in the vegetable field topsoils was poor except bacteria, especially fungi and actinomycetes which existed only a little in subsoils. The bacteria/fungi ratio of the vegetable field soils in Tianjin were much higher than those of the vegetable field soils in Kochi University. The 3 species of fungi, which have poor or rich saprophytic activities, grew well on the vegetable field soils after incubation in petri dishes. These results showed that almost all of the vegetable field soils in Tianjin had the ability of providing a nutrient source for microorganisms and it will be possible to develop good soil fertility by improving the manuring practices and environmental conditions.

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Effect was investigated of spraying electrolyzed strong acid water (ESAW) obtained by electrolysis of a NaCl dilute (ca. 50mg L^-1) water solution on the incidence of downy mildew (Pseudoperonospora cubensis Rostowzew) in cucumber (Cucumis sativus L, cv. Naoyoshi) grown in a plastic house. pH, free effective chlorine concentration and oxidation-reduction potential of the ESAW were 2.8, 32 ppm and 1 120 mV, respectively. Different amounts of either the ESAW (0.25, 0.5 or 1 L plant^-1) or well water (0.5 L plant^-1) were sprayed onto the leaves once every third or, fourth day. The incidence of downy mildew was controlled almost perfectly for the experimental period of 17 d by spraying the ESAW, regardless of the amount sprayed, while the symptom of downy mildew was observed on day 10 with well water and on day 13 with non-treated control. On day 17, the incidence was significantly reduced by spraying the ESAW (0 or 2%) as compared to both well water (48%) and non-treated control (32%) . However, spraying the ESAW caused a leaf burn-like physiological disorder in some leaves after day 7, regardless of the amount sprayed. The results indicate that ESAW can be a viable alternative to some fungicides to control several crop diseases, or it can at least be effective in reducing fungicide use ; however, there remains the problem of eliminating the leaf burn-like physiological disorder.

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The role of Ca²⁺ and protein phosphorylation in glycerol dissimilation under hypoosmotic stress in the halotorelant alga Dunaliella was investigated by a pharmacological approach. A stretch-activated Ca²⁺ channel blocker, GdCl₃, inhibited glycerol dissimilation under hypoosmotic stress. Glycerol dissimilation under hypoosmotic stress was also inhibited in the presence of protein kinase inhibitors, K-252a and staurosporine. K-252a and staurosporine potently inhibits several types of protein kinase including serine/ threonine- and tyrosine-type protein kinases. Erbstatin analog (metyl 2, 5-dihydroxy-cinnamate), a specific inhibitor of tyrosine-type protein kinase, however, had no effect on glycerol dissimilation under hypoosmotic stress. The results of the present study suggest that Ca²⁺ influx from the extracellular space and protein phosphorylation by K-252a- and staurosporine-sensitive protein kinase (s) appear to be participate in the process of glycerol dissimilation under hypoosmotic stress in Dunaliella.

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