In a pot experiment under controlled condition, tomato (Lycopersicum esculentum Mill.) plants were grown for 28 days under five different soil moisture regimes (SMRs), viz. non-irrigated, and irrigated up to container capacity (CC) level allowing 60, 45, 30, and 15% depletion of CC moisture (DCCM) . The plants showed a higher weekly average evapotranspiration (ET) rate, and a higher cumulative ET after 28 days after transplanting (DAT) when more water was made available in their root zone through irrigation. Biomass production in different plant parts and water use efficiency increased significantly with frequent irrigations allowing minimum soil drying from CC level. High sensitivity of the crop to soil moisture stress was indicated by a significant reduction in biomass production when irrigations were given allowing more than 15% DCCM. Nitrogen dilution effects in different plant parts were observed for the wetter SMRs. However, total N uptake was remarkably enhanced with increased availability of soil moisture. Significant and positive correlations of biomass production with water use and N uptake were noted. A soil moisture regime that allows up to 15% DCCM for irrigation performed best with regard to biomass production and nitrogen uptake as well as agronomic efficiencies of water and nitrogen. The findings merit considerable significance to irrigation scheduling and water management for maximizing tomato yields.

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Utilization of rice husk charcoal as a soil aerating material to increase tuberous root yield of sweetpotato [Ipomoea batatas (L.) Lam.] under field conditions in a wet lowland was investigated. The rice husk charcoal was applied to ridges in the field in two ways ; the material was placed in the central layer of the ridge without mixing with soil (unmixed material treatment), or the material was thoroughly mixed with the ridge soil (mixed material treatment) . Water depth between the ridges was kept at 20 mm above the furrow level throughout the growing period in order to imitate the wet soil conditions in tropical and subtropical lowlands. A conventional ridge without the material was set as a control. The fresh and dry weights of the total phytomass were greatest in the unmixed material treatment. The fresh and dry weights of above-ground parts in the unmixed material treatment were approximately 0.6 times those in the control, while the weights of subground parts in the unmixed material treatment were approximately 4 times greater than those in the control. The unmixed material treatment gave a dry weight of tuberous roots that was 6 times greater than the control. The main stem length and leaf area were smaller in the unmixed material treatment than in the mixed material treatment and the control. Water content of tuberous roots and the shoot-root ratio were lower in the unmixed material treatment than in the control. Plants in the unmixed material treatment had a greater biomass of edible parts (tuberous roots) and a smaller biomass of non-edible parts (stems, leaves and roots other than tuberous roots) than did those in the control.

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Effect of pre-exposure light on the first positive phototropic curvature in dark-grown radish seedlings (Raphanus sativus L. cv. Miyashige) was investigated. When the seedlings are pre-exposed to white-light from above, the magnitude of the first positive phototropic curvature of the hypocotyls responding to unilateral blue-light pulseirradiation was enhanced. The pre-exposure treatment to the hypocotyls only accelerated the development of the phototropic curvature. Treatment to the apex and cotyledons had no effect on the increase of the phototropic curvature. These results suggest that the pre-exposure treatment enhances the first positive phototropic curvature of the dark-grown radish seedlings, and the pre-exposure light may be perceived by the phototropic responding organ, the hypocotyl itself.

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This study primarily deals with the mangrove forest, which is mainly composed of Rhizophora stylosa and Bruguiera gymnorrhiza, and is located in Iriomote Island. Its focus was the mechanism which Rhizophora stylosa and Bruguiera gymnorrhiza represent in the visible zonation pattern. The change of chemical elements of soil water and leaves were analyzed to clarify the mechanism. As a result, B and Ca of the leaves of Rhizophora stylosa showed correlations with the soil water EC at a depth of 60 cm. On the other hand, the elements of the leaves of Bruguiera gymnorrhiza that showed correlations with the soil water EC were N, P, S, Ca, Mn, and Fe. Particularly, the change of B content of Rhizophora stylosa and Mn content of Bruguiera gymnorrhiza were assumed to be restrictive factors in the zonation pattern of mangroves.

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For Closed Ecological Life Support Systems (CELSS), the oxygen regeneration system is very important because it produces oxygen, one of the most essential materials for human life support. In order to develop an oxygen regeneration system based on algal culture, it is important to find the relationship between the oxygen production rate and the culture conditions. The light conditions in algal suspensions have not been studied in-depth, because analysis of light intensity in an absorption-scattering medium, like an algal suspension, is very difficult. In this study, the light intensity distribution in a suspension of Spirulina platensis, a common blue-green alga for CELSS, was analyzed by using the radiative transfer equation, and absorption and scattering coefficients by approximation methods. In a comparison between calculated and measured values, the calculated intensities did not agree to the measured light intensity. Suitable values for the absorption coefficient and the scattering coefficient which resulted in agreement between the calculated and measured values were selected by iterative calculations.

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It has been known that water uptake of plant roots is depressed under hypoxia in hydroponics. In this study, lignification in hypoxic roots of cucumber plants was histochemically investigated. Cross sections of the secondary roots were treated with lignin-specific stain, phloroglucinol-HCI (Weisner reaction) . The cortical cell walls around the vascular cylinder were clearly stained in the hypoxic roots, but scarcely stained in the roots grown in well-aerated nutrient solution. From the fact, it is considered that lignification of the cortical cells around the vascular cylinder of the hypoxic roots may be one of the factors causing depressed water uptake.

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