Activities of β-N-acetylhexosaminidase and chitobiase were measured in maturing and germinating seeds of Phaseolus vulgaris L. cvs. Suratto-wands and Maisugata. The chitobiase activity became higher when embryos began to develop prior to rapid fresh weight increase in seeds, and decreased rapidly when seeds began to increase their fresh weight rapidly. When the seed growth was inhibited by low temperature, the chitobiase activities decreased dramatically in developing seeds. The β-N-acetylhexosaminidase and chitobiase activity patterns were different between the two varieties, and did not exhibit clear correlation with growth and development of seeds in both varieties. Additionally, the β-N-acetylhexosaminidase activities were not sensitive to changes in seed growth and development affected by low temperature. In dry seeds, the chitobiase activities were not detected, and when seeds germinated, its activities became apparent. The β-N-acetylhexosaminidase activities were present in dry and germinating seeds, and had similar values in Suratto-wanda and Maisugata. Although β-N-acetylhexosaminidase and chitobiase have been known to be the same group of enzymes in general, the present study suggests that they are different, and that chitobiase may be one of key enzymes related to seed development and germination processes.

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In order to investigate the effect of light-dark cycles on growth of Cassia nomame, plants were grown under 5 different light-dark cycles for 288 h that were 12h cycle (6L-6D), 18h cycle (9L-9D), 24 h cycle (12L-12D), 36 h cycle (18L-18D) and 48 h cycle (24L-24D) . The growth of plants under 24 h cycle was the best of all, those under 36 h cycle and 48 h cycle were the worst and those under 12 h cycle and 18 h cycle were medium. The leaves of C. nomame move under natural light-dark cycle, then we examined the leaf movement under the same light-dark cycles described above. The plants grown under 24 h cycle kept their regular and steady leaf movement, but ones under other cycles could not keep their regularity. It is natural to think that leaves moved under the control of endogenous rhythm and plants under light-dark cycles except 24 h had unsteady endogenous rhythms. These results suggest that the best condition of light-dark cycle for growth is one that helps plants keep their own endogenous rhythms.

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To prevent high temperature or to reduce the cooling load in grenhouses in the daytime during a high temperature period has been one of the most important problems to be solved for protected horticulture, especially in Japan. Therefore the authors have worked at the development of an effective shading material against infrared radiation (or thermal rays) which doesn't contribute to photosynthesis. This report examines the effect on the reduction of cooling load in the daytime of a newly-developed covering material, named “Filter” by the authors. The main results obtained are as follows : 1) Filter cut about 60% of shortwave radiation and 30% of photosynthetic photon flux density (PPFD) . 2) When the total shortwave radiation incident on the covering material was 618 W/m² and the cooling load under existing clear glass was about 500 W/m² at inside air temperature of 25°C, the cooling load under Filter was reduced by 180 W/m² in comparison with that under clear glass, and by 50 W/m² in comparison with the case of clear glass with 20% shading so as to agree with the value of PPFD under Filter. 3) The effect of cooling the covering material on the reduction of cooling load was remarkable with Filter. The reason is that the temperature of Filter is relatively high and thermal radiation emitted from Filter to the inside is comparatively large, because of absorbing a considerable part of infrared radiation.

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Changes of individual lipids and their fatty acid composition in flowers and fruitlets of Japanese pear ‘Nijisseiki’ were measured during the periods of flowering and fruit setting in 1995 to investigate their role in cold hardiness and reproductive growth. Following the increase of air temperature from flowering to fruit setting, cold hardiness decreased with the proportion variations of lipids and fatty acids. All kinds of individual galactolipids and phospholipids, especially phosphatidylcholine (PC) and phosphatidylethanolamine (PE), declined gradually after full bloom. The proportion of linolenic acid (C18: 3), as one of the most abundant fatty acids in flowers and fruitlets of pear, sharply declined about 25% in total lipid and more than 10% in phospholipids and galactolipids during the period of fruit setting. Significant increases of linoleic acid (C18: 2) in monogalactosyl diglyceride (MGDG), phosphatidic acid (PA), PC and PE and palmitic acid (C16: 0) in digalactosyl diglyceride (DGDG) and phosphatidylinositol (PI) occurred simultaneously. The decline in unsaturation of lipids resulted in lower level of cold hardiness in pear flower and fruitlet.

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Bulblets regenerated on the scale of Lilium japonicum Thunb. are induced into dormancy during in vitro culture. We conducted the experiment to know the effects of cold temperature, 24-epibrassinolide (EB) and light on breaking of the dormancy of the Bulblets. 1. The rate of leaf emergence from the small bulblets (35 to 50 mg, FW), pre-treated at 4°C for 8 weeks and cultured on MS-medium without plant hormones under light, was 85%. 2. The rate of leaf emergence from the large bulblets (1 to 2 g, FW), without cold treatment and cultured on MS-medium containing 0.1 ppm EB, was 54%. However the bulblets, which were pre-treated at 4°C for 10 weeks and cultured on media containing 0.1 and 1 ppm EB under light, showed 100% of leaf emergence. 3. After the bulblets were cultured on the media under the light or the dark in vitro and treated at 4°C for 10 weeks, they were transplanted into pots. The rate of leaf emergence from the bulblets grown under the light was higher than the dark. But dormancy of the bulblets both under the light and the dark wasn't completely broken out. After the bulblets were harvested from the pot and re treated at 4°C for 10 weeks, they were retransplanted into a new pot. The bulblets both under the light and the dark indicated 100% of leaf emergence.

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Germination and emergence tests were carried out to examine the effectiveness of pericarp removal in spinach seeds. The seeds were classified into five groups according to their weights, and the germination was investigated in different concentrations of NaCl (0, 50, 100, 150 and 200 mM) or mannitol solution (-0.25, -0.49, -0.73 and -0.98 MPa) . For the emergence test, the seeds were sown at the depth of 1.5 cm in sand soil containers. The germination exceeded in pericarp-removed seeds. It declined and delayed with increased NaCl concentration. Emergence also declined with increased NaCl concentration. The removal of pericarp in spinach seeds was found to be effective for germination and emergence even in NaCl solutions.

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The effects of heavy metals on ethylene release from plants were investigated and the possiblity of plant growth diagnosis by measuring the enthylene concentration in closed plant cultivation systems such as Controlled Ecological Life Support Systems (CELSS) was discussed. The ethylene release rate of intact lettuce plants (Lactuca sativa L. cv. Okayama) was increased by 0.34 mmol L^-1 of Ni and 0.34 mmol L^-1 of Co and decreased by 0.38 mmol L^-1 of Cr and 0.31 mmol L^-1 of Cu. Chlorophyll degradation in the leaves occurred in the unexpanded leaves in Ni treatment and in the expanded leaves in Co treatment. In these leaves, ethylene was mainly produced. No visible injury was observed in Cr and Cu. The time course of ethylene concentration was investigated in a closed chamber in which 12 lettuce plants were hydroponically cultivated with a nutrient solution containing 0.34 mmol L^-1 of Ni. The ethylene concentration in the chamber started to increase 18 h after the beginning of the experiment. Thereafter, it continued to increase and the highest value (8.0 nmol h^-1/plant) was observed 30 h after the beginning of the experiment. This change was more drastic than those in rates of photosynthesis and transpiration, and occurred earlier than appearance of visible injury by Ni stress. These results indicate that measurement of ethylene concentration in closed systems such as CELSS can be a useful non-destructive measurement method for plant growth diagnosis.

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Growth and photosynthesis of the photomixotrophically grown cauliflower plantlets (Brassica oleracea L.) were investigated during a 1-week in vitro culture under naturally ventilated conditions followed by a 2-week ex vitro acclimating period. The in vitro generated leaves in a ventilated vessel had higher rates of photosynthesis than those in an airtight vessel. The enhanced rates of photosynthesis in those leaves, which contained both increased amounts of chlorophyll and total soluble protein, contributed to promote the growth in vitro and the acclimation of plantlets to ex vitro. A nearly half concentration of ambient CO₂ was kept in a naturally ventilated vessel, in which the plantlets grew well by positive photosynthesis during the photoperiods. Both the leaf expansion and the shoot and root dry weight increased under higher photosynthetic photon flux density (PPFD, 50 vs. 100μmol m^-2 s^-1) during the ventilated in vitro culture period. In the first two weeks after transplanting the cauliflower plantlets, the high photosynthetic capacity of in vitro generated leaves had an important contribution to the unfolding of acclimating leaves and the successful acclimation of the whole plantlets.

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For the production of iron-enriched leaf vegetables, increasing the foliar iron content by soaking the roots of leaf vegetables in an ammonium ferric citrate solution, prepared with two levels of pH and iron concentration, was investigated in a climatron (temperature: 27°C; relative humidity : 45-55%; PPFD: 380μmol m^-2 s^-1) . Injuries appeared on the leaves of garland chrysanthemum (Chrysanthemum coronarium L.) in all the treatments and on the leaves of spinach (Spinacia oleracia L.) when soaked in Fe-100 mg L^-1 solution with pH 3 and pH 4 for 24 h. In all leaf vegetables, the foliar Fe content on leaves was higher in the pH 3 treatment than in the pH 4 treatment when soaked in the solution of the same Fe concentration and was higher in the Fe-100 mg L^-1 treatment than in the Fe-50 mg L^-1 treatment when soaked in the solution of the same pH. The foliar Fe content of leaf onion (Allium fistulosum L.) treated with the Fe-100 mg L^-1 solution with pH 3 for 24 h showed its maximum (79.5±9.3 mg kg^-1 fresh weight) and was about 8.0 times that of the control. The spinach treated with the Fe-50 mg L^-1 solution with pH 3 for 24 h showed the maximum foliar Fe content (102.7±12.5mg kg^-1) without damage and its value was about 10.0 times that of thee control.

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A machine vision system which used macroscopic images of carrot cell suspensions was developed. This system was used to non-invasively evaluate cell growth. Packed cell volume (PCV) of the suspension was estimated by two features extracted by image analysis using the B component of the RBG color image. One feature was the number of pixels which were extracted by thresholding the B component at an appropriate value. It represented projected area of cells and cell aggregates, and could be used for PCV estimation. Another feature was the sum total of B values of all pixels in the suspension image. It was also used for PCV estimation having the advantage that it did not require a procedure for extracting pixels corresponding to cells. Using this system, an increase in specific growth rate with a decrease of embryogenic potential was monitored in a carrot embryogenic cell suspension culture. This system showed the potential to be used to select cell lines with desirable growth characteristics for somatic embryo production.

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The net photosynthetic and evapotranspiration rates, and sensible and latent heat transfer rates of tomato plug sheets consisting of plugs, soil mix and a tray in a greenhouse were estimated continuously. Absolute humilities (q₁ and q₂), CO₂ concentrations (C₁ and C₂) and air temperatures (T₁ and T₂) were measured at two heights (z₁ and z₂, respectively) above the plug sheets with a dew point analyzer, an infrared CO₂ analyzer and thermocouples. The weight of the plug sheet was also measured with an electronic balance. The evapotranspiration rate, E, was determined based on the difference between weights of the plug sheet at time t-Δt/2 and t+Δt/2. The diffusion coefficient, K, was determined based on E and the absolute humidity gradient with the equation E=-K (q₂-q₁) / (z₂-z₁) . The net photosynthetic rate was determined from the CO₂ gradient, (C₂-C₁) / (z₂-z₁), multiplied by K. The sensible heat transfer rate was determined from the air temperature gradient, (T₂-T₁) / (z₂-z₁), multiplied by K and the heat capacity of the air. The latent heat transfer rate was determined from the evapotranspiration rate multiplied by the latent heat of vaporization. This technique was useful to estimate the rates of net photosynthesis, evapotranspiration and the sensible and latent heat transfers of plug sheets under the growing conditions in the greenhouse.

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Micropropagation of toad lily (Trichyrtis hirta Hook.) was achieved by subculturing stem-sections with nodes and divided axillary shoots on Murashige and Skoog (MS) basal medium with 0, 0.44 or 4.4μM N⁶-benzyladenine (BA) . A proliferation rate of 3.1 microcuttings per 17-d interval was achieved on the medium with 4.4μM BA. Shoots elongated from these in vitro cultured explants could be rooted at the frequency of 90% on the MS medium with 0.49μM indole-3-butyric acid (IBA) . Plants were readily acclimatized in the soil and flowered normally after transfer to a greenhouse.

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