An investigation was carried out to ensure the proper water quality by using natural minerals that have electrochemical functions (i.e.Quartz Porphyry and ceramics made from Quartz Porphyry) . One type of ground water and Dhaka tap water from Bangladesh and Kochi tap water of Japan were used in various treatments. The treatments with ceramics and Quartz Porphyry significantly changed the physical properties of water, but small changes in chemical components of water were found after the treatments. The values of pH, oxidation-reduction potential (ORP) and surface tension (ST) in ceramics treated Kochi tap water and Dhaka tap water ranged around levels suitable for plant growth, while these values of the treated ground water of Bangladesh did not range around the suitable levels. Germination test with Komatsuna plants (Brassica rapaL. nothovar) was conducted to examine effects of the treated water on early plant growth. Ceramics treatments for Kochi tap water and Dhaka tap water significantly activated the early growth of Komatsuna plants. These results suggest that ceramics treatments of Kochi and Dhaka tap water can be expected as advantageous in controlling the growth of plants.

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Cultivars with different spikelet weight were compared with the ripening characteristics of primary and secondary spikelets at different positions in panicle and discussed the relation of the ripening process and dry matter production. The objectives were to know the variations of grain filling process of both primary and secondary spikelets among different grain size cultivars. Second, to find out the main ripening period (MRP, the accumulation period from 15.9-84.1% of the maximum grain weight) with the rate of grain filling and which factor between these two are important for the determination of final grain weight. The MRP of different grain size cultivars groups varied from 14-21 (small), 15-21 (medium), and 16-21 d (large) . The dry weight accumulation rate of a spikelet (DWAR-S) during MRP ranged 0.404-0.720, 0.624-0.981 and 0.703-1.297 mg/spikelet/d in small, medium and large grain cultivars, respectively. Among all cultivars MRP of primary and secondary branch spikelets were 13-16 and 14-23 d where DWAR-S were 0.672-1.544 and 0.334-0.939 mg/spikelet/d, respectively. The larger spikelet weight was accompanied with the faster rate of accumulation and a slower rate enhances the MRP. The relations between DWAR-S during MRP and a final spikelet dry weight showed significant positive correlation (r=0.834^***) but no significant correlation was observed between the days of MRP and the final spikelet dry weight (FSDW) . Further, the temperature and radiation showed insignificant relationship with DWAR-S during MRP and for the same temperature the DWAR-S varied much among the cultivars which indicated that the FSDW was controlled mainly genetically with a partial impact of environment. It could be concluded that the large grain cultivars gained the higher spikelet weight at a faster rate of accumulation and not to the long period of accumulation.

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This study was conducted to determine the effects of soil nitrogen levels (0.22, 0.44 and 0.88gN pot^-1) on the heterosis for photosynthetic characters, dry matter production and grain yield in F₁ hybrid rice obtained from thermo-sensitive genic male sterile line. Net CO₂ exchange rate (CER) and other related characters viz., SPAD reading, leaf N content, soluble protein content and ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) activity increased significantly with increasing N level in all the F₁ hybrid and parental cultivars. With increasing N level, the number of tillers, leaf area, root weight, wholeplant dry weight and grain yield also increased. Under the low N level, the F₁ hybrid did not show heterosis for most photosynthetic characters. However, at high N level, heterosis for CER over both the male parent and the mean of parents was ascribed to high leaf N content and several characters related to CER. The F₁ hybrid exhibited substantial heterosis over the male parent for whole-plant dry weight, number of panicles per plant, number of spikelets per panicle and grain yield in all N levels. Among the yield components, the strengthening of heterosis for number of filled grains per panicle was the major cause of greater heterosis for grain yield in the F₁ hybrid at high N level.

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Cucumber (Cucumis sativus L.) seedlings were grown at high (85-90%) or low (12-25%) relative humidity (RH) for 6 days. Air temperature was 29-31°C. Seedlings of each regime were then transferred for 1 day to high or low RH condition. Transpiration rates and leaf conductance of the seedlings were then measured at RH of 40-50% and air temperature of 28°C. In seedlings transferred from high to low RH, transpiration rates and leaf conductance were lower ; also, growth of their cuttings after planting was higher compared to the seedlings kept at high RH for 7 days. In seedlings transferred from low to high RH, transpiration rates and leaf conductance were higher ; also, growth of their cuttings after planting was smaller compared to the seedlings kept at low RH for 7 days.

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Plants of radish ‘Taibyo-sohbutori’ were exposed to the low temperature treatment (6°C) with an interruption of high temperature (17, 24 or 30°C) for 4, 6 or 8 hr per day, respectively. We applied a new index “flower formation index” to the data of floral induction after the treatment in order to estimate hours per day contribute to devernalization and vernalization. According to “flower formation index”, the inflorescence formation suppressed under the high temperature treatment at 24°C for 6 to 8 hr per day, and this suppression markedly occurred at higher temperature of 30°C. In the case of intermittent low temperature treatment, by calculating “estimated hours per day contribute to vernalization and devernalization”, it was possible to recognize the effect of high temperature interruption during low temperature treatment. We supposed that the vernalization effect by a low temperature treatment would be counteracted by 30-40%, if the plants are exposed to 24°C for 8 hr or 30°C for 6 hrs per day during the low temperature treatment.

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Grafted tomato (scion : Lycopersicon esculentum Mill. cv. House Momotaro ; rootstock : cv. Kagemusha) plug seedlings were stored for 35 d at 10°C under total photosynthetic photon flux density (PPFD) of 2μmol m^-2s^-1 using mixed light from red and blue light emitting diodes (LEDs), with different percentages of blue-light PPFD (0%: R100, 2%: R98B2, 5%: R95B5, 10%: R90B10, and 50%: R50B50) . The stored seedlings were transplanted and then cultivated for 28 d at 27°C and 290μmol m^-2s^-1 PPFD from white fluorescent lamps during the 12h light period and at 18°C during the 12h dark period. The effect of blue-light PPFD percentage was investigated and the best percentage was synthetically determined based on 5 and 8 items for the last days of storage and cultivation, respectively. An improving tendency was observed by increasing the percentage of blue-light PPFD in visual quality scores and leaf area on the last day of storage, aerial- and subterranean- part dry weights on the last day of cultivation. There was no applicable tendency in other items with increasing the percentage. It can be concluded that the 50% of blue-light PPFD was the best percentage among the tested ones and increasing the percentage up to 50% contributed to quality improvements for low light irradiation storage of grafted tomato plug seedlings at 10°C and 2μmol m^-2s^-1 PPFD from red and blue LEDs.

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Tomato (cv. Momotaro) seedlings with cotyledons were grown under three different alternation of light and dark periods for 14 days. In each treatment, the light period began at the same time of day every day. In the periodic alternation treatment (P), both the light and dark periods were 12 h for each day. In one of two non-periodic alternation treatments examined in the present study (ND-1), the number of hours in the light period was a random integer between 6 and 18 subject to the provision that the average light period per day during the experiment was 12h. The dark period was adjusted to make the period 24h. The other non-periodic alternation treatment, ND-2, was similar to ND-1 except that the random integer was between 1 and 23. The standard deviations of the light periods (SD) were 0h in P, 4h in ND-1, and 6h in ND-2. At the end of the experiment, dry mass and leaf area per seedling were greater in P than in ND-1 and ND-2, while stem length was shortest in P, followed by ND-1 and ND-2. Flower-bud initiation was earliest in ND-2 and the number of leaves preceding the first flower truss differentiation was lowest in ND-2, followed by ND-1 and P. When SD is used as the independent variable, stem length increased and leaf area and the number of leaves preceding the first flower truss differentiation decreased with increasing SD. In this study, plant growth and development were not necessarily better when the alternation of light and dark periods was periodic than when it was non-periodic.

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Rice (Oryza sativa L. cv. Soja-Akamai) seedlings accelerated the growth of roots of alfalfa (Medicago sativa L.) seedlings when both seedlings were grown together. Growth promoting activity was found in the culture solution in which the rice seedlings were hydroponically grown for 15 d. These findings suggest that this cultivar of rice may produce and release a growth promoting substance into the culture solution or neighboring environment.

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Tomato (Lycopersicon esculentum Mill., cv. Momotaro) seedlings were grown in 70% or 10% relative humidity (RH) for 10 d. Then, their cuttings with 3-4 foliage leaves and two cotyledons each were stored for 28 d in air temperature of 10°C with photosynthetic photon flux density of 4μmol m^-2s^-1 and RH of more than 95%. Nutrient solution was supplied to the cuttings through the stem cut-ends during storage. Before storage, the percentage of water content of cuttings from seedlings grown in 10% RH was significantly lower than those from seedlings grown in 70% RH. However, RH had no effect on the cuttings' dry weight, stem length, stem diameter, leaf area, and relative chlorophyll content of the foliage leaves. After beginning storage, no wilting was observed in the cuttings from seedlings grown in 10% RH; in contrast, wilting was observed in the cuttings from seedlings grown in 70% RH. On the last day of storage (Day 28), the percentage of marketable cuttings from seedlings grown in 10% RH was 100%, whereas those from seedlings grown in 70% RH was 5%. These results indicate that 10% RH during tomato seedlings growth reduced environmental stress of their cuttings, and decreased the percentage of less marketable cuttings after beginning storage, in comparison with 70% RH.

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