There have been several reports on the effects of various photoperiods on flowering in Capsicum annuum, but few on such effects on other species of the genus Capsicum. In this study, the flowering under various photoperiods of two C. frutescens lines from the Bonin and Ryukyu Islands in Japan and C. annuum cv. ‘Takanotsume’ (referred as BON, RYU, and TK, respectively) was investigated. The main differences in flowering between C. frutescens and C. annuum were evident under long-day photoperiods. TK plants grown under photoperiods longer than 15 h bore flowers normally, whereas BON and RYU plants grown under the same conditions did not bear flowers at first, because their buds failed to grow, and eventually aborted. BON plants bore flowers under a 24-h photoperiod, although the time to flowering was much longer than that for TK plants, but RYU plants exposed to photoperiods longer than 14 h bore no flowers during the entire experimental period. Therefore, long-day photoperiods strongly inhibit C. frutescens flower bud growth, and there are interspecific differences in flowering between C. frutescens and C. annuum and intraspecific differences in flowering between the two C. frutescens genotypes.

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In the present research, the psychological state of elderly people in the process of raising plants from seedlings and bulbs was analyzed by means of brain waves and the semantic differential technique. Subjects were ten elderly individuals and ten young individuals. Each subject raised four kinds of plants (hyacinth, pansy, Italian parsley and candelabra cactus) for ten weeks in his or her house. Subjects raised the hyacinth from bulbs and the pansy from seedlings. At the starting, second, sixth, and tenth weeks of the experiment, the psychological state of the subjects upon seeing their plants in front of them was evaluated. The ratio of alpha waves to beta waves was calculated as an index of the degree of calmness of psychological state. In the elderly subjects, the differences in the ratios of alpha waves to beta waves between the evaluated plants became smaller over time. The influence of the bloom of the pansy on the elderly subjects' psychological state was observed. An increase in the second factor score of the pansy evaluated by the elderly subjects was also observed and this indicated that the elderly people's psychological state was changed by the blooming process of the plants.

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Explants obtained from the terminal buds of edible canna (Canna edulis Ker-Gawl.) were aseptically cultured with different combinations of auxins (NAA, IBA), cytokinins (BA, KN, 2ip), and culture media (B5, 1/2MS, MS), to establish a tissue culture system for this species. The combination of NAA or IBA with BA induced optimal explant growth, and when the explants grew substantially, TIBA promoted lateral shoot growth. For explant growth, the optimal concentration of NAA was 0.1∼0.5 mg L^-1, irrespective of the BA concentration adopted, and the optimal concentration of BA was 0.5∼1 mg L^-1. Some of the explants formed callus-like or protocorm-like tissues. Among the three culture media, B5 gave the highest survival rate of explants (92%), followed by 1/2 MS (72%) and MS (52%). In these combinations, micronutrients followed by macronutrients and vitamins, were found to be most important components for explant survival. Gellan gum at 2.5 g L^-1 was a superior supporting/gelling material for explant growth compared to a filter paper-bridge with liquid medium or 4 g L^-1 agar. Our results indicate that multiple plantlet propagation can be performed routinely, while callus formation remains a time-consuming endeavor.

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Salt stress has been applied to improve the quality of tomato fruit, but ascorbic acid (ASA) and dehydroascorbic acid (DHA, oxidized form of ASA) contents in salt-stressed fruit have not been clearly understood. We examined the salt-induced changes in ASA and DHA contents of tomato fruit in two cultivars and two cropping seasons. Tomato plants were grown under closed irrigation systems in a greenhouse. Salt stress was applied by adding 50 mM and 100 mM NaCl to the nutrient solution. The results indicated that the ASA and DHA contents are not always increased by salt stress, and the effect depends on cropping seasons and cultivars. In the spring-summer season, the ASA and DHA contents in ‘Mini Carol’ (cherry type cultivar) decreased with an increase in the NaCl concentrations, whereas those in ‘House Momotaro’ (normal-fruited cultivar) increased. However, in the fall-winter season, the ASA and DHA contents in both the cultivars increased by salt stress. In addition, our data revealed that salt-induced changes in the ASA and DHA contents were not induced by changes in the ASA precursor, and suggest that, according to cultivars and cropping seasons, these changes may relate to the antioxidant systems against salt-induced oxidative stress.

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The objective of this study was to increase the formation rate of embryos from suspension cultures of Taranoki (Aralia elata). The suspension cultures were prepared from leaf-derived calli. Of the various culture durations, 30 days of culture yielded the best growth of cell suspension cultures in a BT liquid medium supplemented with 2,4-D. Somatic embryogenesis has never been observed without the addition of exogenous plant growth regulators (PGRs). The highest percentage of somatic embryo formation (93.3%) was observed in a BT liquid medium supplemented with 1.0 μM BAP+5.0 μM 2,4-D. The PGR-free semi-solid BT medium showed the highest regeneration frequency of cotyledonary-shaped embryos (100%).

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Aeration and heating were used to improve the disinfection activity of slow sand filtration of recirculating nutrient solutions in a closed hydroponic system. Filter performance was evaluated under different running conditions using E. coli elimination efficiency as an indicator of filter performance. Aeration with or without heating during filter ‘ripening’ increased filter performance so much as to obviate differences in performance associated with filtration rate. The filter reduced influent E. coli concentrations by nearly 3 orders of magnitude with aeration. Effluent E. coli concentrations from filters pre-circulated with aeration and heating were over 4 orders of magnitude lower than influent concentrations. Vertical distribution of viable E. coli in an effective slow sand filter which reduced E. coli concentrations from 10⁶ cfu ml^-1 to less than 10² cfu ml^-1 was mostly in the Schmutzdecke (10⁶∼10⁷ cfu g^-1) and first 10 cm of the surface of the sand layer. High-performance filters did not eliminate Ralstonia solanacearum as effectively as E. coli or the fungal pathogens Fusarium oxysporum and Pythium helicoides.

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The effects of light quality on biomass and internal quality of leaf lettuce, spinach and komatsuna were examined. The plants were grown hydroponically in an environmentally controlled room with a 12-h light period and under a light/dark temperature of 20±1°C/18±1°C and a photosynthetic photon flux density (PPFD) of 300 μmol m^-2 s^-1 under four light quality treatments, i.e., red light from red fluorescent lamps (R) or blue light from blue fluorescent lamps (B) or a mixture of R and B (RB) or white light from white fluorescent lamps (W). The irradiation of R compared with W increased shoot dry weight in komatsuna and decreased the nitrate content in spinach. Irradiation of B or RB compared with W increased the L-ascorbic acid content in leaf lettuce and komatsuna and decreased the nitrate content in leaf lettuce. Irradiation of B was not suitable for the spinach cultivation due to an extremely decreased shoot dry weight although the carotenoid content was slightly increased. Our data show that controlling light quality is useful to achieve higher productivity or higher nutritional quality of the commercial crops even under limited light intensity in controlled-environment agricultural facilities although the effective light quality treatment differs depending on the plant species.

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