The objective of this research was to experimentally determine whether signs of water deficit stress in plants can be detected from changes in the absorbance spectra based on the relationships between absorbance spectra and physiological parameters. Absorbance of tomato leaves in the near-infrared (NIR) wavelengths (1100 nm to 2500 nm) was measured simultaneously with photosynthesis and stomatal conductance during water stress. To observe small changes in absorbance which arise from water stress, a leaf in non-stressed conditions was used as a reference for the absorbance measurements. In general, under the effects of water stress, peaks formed in the absorbance spectra at water absorbance bands near 1 440 nm and 1 940 nm, and absorbance decreased near 1 600 nm forming a valley. Although the relationship between the changes in absorbance and physiological parameters varied depending on the individual plants tested, consistent overall trends were observed, demonstrating there is potential to nondestructively detect changes in plant condition resulting from water stress by measuring NIR absorbance.

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The effects of photoperiod and CO₂, concentration on the bolting of Spinacia oleracea transplants were investigated. Shoot and root dry weights of the transplants increased significantly with increasing CO₂ concentration. The floral development of transplants grown under a 14-h·d^-1 photoperiod were more progressed than those grown under a 10-h· d_-1 photoperiod. However, the progress of floral development was similar for the transplants grown under different CO₂ concentrations if the photoperiod was the same. More than 80% of the plants in the treatments with the 14-h·d^-1 photoperiod bolted 3 d after transplanting (DAT), while none of the plants in the 10-h·d^-1 treatments bolted at this time. At harvest (14 DAT) the percentage of the plants that bolted was greater than 80% in all treatments. Between treatments with the same CO₂ concentration, the flower-stalk length of plants at harvest in the 14-h·d^-1 photoperiod treatment were greater than those in the 10-h·d^-1 treatment. Among plants in the same photoperiod treatment, flower-stalk lengths were not significantly affected by CO₂ concentration after they were transplanted to a 16-h·d^-1 photoperiod. These results show that the delay of bolting that occurs with shortening the photoperiod during transplant production was due to the delay of floral development and not to retarded vegetative growth.

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This study was undertaken to evaluate the efficiency of electrolyzed water for controlling rice blast disease caused by a fungal pathogen, Magnaporthe grisea. Inoculation experiments were performed using three races (007, 017 and 303) of M. grisea as the inoculum and two cultivars (Koshihikari and Nakate-shinsenbon) of rice (Oryza sativa L.) as the hosts. The percentage of conidial germination of the fugus in electrolyzed acid water and alkaline water was significantly decreased compared to that in distilled water. Electrolyzed acid water and alkaline water showed suppressive effects against the disease when they were sprayed to leaves 1 d before the inoculation of conidia, but they were ineffective when sprayed 1 d after the inoculation. The suppressive effect of electrolyzed acid water and alkaline water against rice blast disease was smaller than that of a fungicide. Electrolyzed acid water and alkaline water showed the similar protective effect against the disease. These suggest that both of electrolyzed acid water and alkaline water have a high suppressive effect against rice blast disease when they are sprayed on rice plant before the pathogen penetrates into plant tissues.

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The effects of water supply and light intensity on the growth of spring wheat (Triticum aestivum L.) was studied under carefully controlled conditions. The leaf water potential (LWP) was measured from 5 to 40 d after the initiation of water supply treatments (DAIT) . The LWP decreased as DAIT progressed. At higher photosynthetic photon flux densities (PPFDs), the LWP decreased as the water supply decreased. The water supply rate had little impact on tiller initiation and survival under low PPFD. As the PPFD increased, however, tillering responded sharply to water supply. Differences in tiller numbers were mainly due to differences in the number of subtillers from T0, T 1 and T2 primary tillers. The water supply rate did not affect plant growth significantly under low PPFD. Increased PPFD resulted in increased plant growth, except for leaf numbers per main stem, as water supply rate increased. Thus, there was a highly significant interaction of water supply and light intensity on the growth of spring wheat.

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Two experiments were carried out to determine the optimum combination of CO₂ concentration and photosynthetic photon flux density (PPFD) under low light irradiation controlled atmosphere (LLI-CA) storage conditions at atmospheric O₂ concentration for the quality preservation of grafted tomato (Lycopersicon esculentum Mill., scion : cv. Momotaro ; rootstock : cv. Helper M) plug seedlings. In the first experiment, the seedlings were placed in a glass vessel at 10°C, and CO₂ exchange rate was measured under different CO₂ concentrations (0.05, 0.5 or 1.0%) and PPFDs (0, 1.0, 2.0 or 3.0pmol m^-2 s^-1) of red light from light-emitting diodes. A 3-dimensional (CO₂ concentration, PPFD and CO₂ exchange rate) graph was drawn to find a curve expressing the relationship between CO₂ concentration and PPFD where the CO₂ exchange rate becomes 0. All combinations of CO₂ concentration and PPFD on the curve are theoretically the most essential conditions for keeping dry weight of the seedlings nearly constant during storage. In the second experiment, grafted tomato plug seedlings were stored at 10°C for 28 d under the following combinations of CO₂ concentration and PPFD selected from the curve : 0.05% + 2.5μmol m^-2 s^-1 (C0.05P2.5), 0.25% + 1.9 μmol m^-2 s^-1 (C0.25P1.9), 0.50% + 1.3 μmol m^-2 s^-1 (CO.SOPL3), 0.75% + 0.9μmol m^-2 s^-1 (C0.75P0.9) and 1.0% + 0.5 μmol m^-2 s^-1 (C1.0P0.5) . Storage conditions of 0.05% CO₂+0μmol m^-2 s^-1 PPFD were used as the control (font) . Five-rank subjective visual quality scores of the seedlings and color difference values of the leaves (ΔEab) on the last day of 28 d storage were in the following order: C0.25P1.9>C0.50Pl.3>C0.05P2.5=C0.75P0.9>C1.0P0.5>Cont and Cont = C1.0P0.5 = C0.75P0.9 = C0.05P2.5>C0.50P1.3>C0.25P1.9 (Cont> C0.05P2.5), respectively (where‘>’ and ‘=’ denote significantly greater and not significantly different at the 5% level by LSD, respectively) . Survival percentages in C0.25P 1.9 and C0.50P1.3 were 100% (10 plants out of 10) on the last day of 28 d cultivation following 28 d storage whereas survival percentages in C0.05P2.5, C0.75P0.9, C 1.0P0.5 and Cont were 90, 70, 20 and 0%, respectively. These results showed that the optimum conditions of LL-CA storage for quality preservation of grafted tomato plug seedlings at l0°C under atmospheric O₂ concentration were 0.25% CO₂ combined with 1.9ymol m^-2 s^-1 PPFD. These results also indicate that there exists a minimum level of PPFD for successful LL-CA storage, and the minimum was considered to be between 0.9 and 1.3, umol m^-2 s^-1 for the seedlings used.

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Applicability of the integrated solarimeter film (Taisei Chemical Co. Ltd., Optleaf R-2D) for the measurement of amount of light-interception by individual leaves in fruit vegetables was investigated. The fading rate of the film was highly correlated with the values measured by an integrated solarimeter at an open field, though the rate was depended on the air temperature during the measurement. Integrated solar radiation in a glasshouse could be estimated by the film as well as at an open field. Amount of light-interception by individual leaves of vertically trained watermelon plants could be measured by the film and light-interception characteristics of the plants could be expressed numerically. The integrated solarimeter film would be useful for analyzing light-interception characteristics in fruit vegetables.

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Some Indole derivatives were examined for their algicidal activity to Chlamydomonas reinhardtii and the isolate of Chlamydomonas sp. which was isolated from the green algae-generating hydroponic solution in the hydroponic trough of the greenhouse. Of nine compounds tested, 3-indolepropionic acid, 3-indoleacrylic acid and 3- (3-indolyl) butanoic acid could suppress multiplication of C. reinhardtii cells. Although the first one exhibited the strong phytotoxicity, the latter two compounds were effective at lower concentrations which did not cause any toxic effect on the growth of tomato seedlings. In addition, 3-indoleacrylic acid and 3- (3-indolyl) butanoic acid inhibited the multiplication of Chlamydomonas green algae which were actively growing in our hydroponic facilities, and suppressed the algal emergence on the synthetic sponge cubes soaked in the hydroponic solution which had been inoculated with green algae. The present study suggests that these compounds have a potential to be used as an algicide for the hydroponics of crop plants.

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