The speaking plant approach (SPA) is regarded as a desirable concept for environmental control in highly sophisticated greenhouses. An important feature of SPA is sensor-based plant diagnostic techniques, which are used to monitor plant physiological status. Although the concept of SPA was originally proposed approximately 30 years ago, the practical application of SPA techniques in commercial greenhouses has only recently become feasible, due to the innovation of easy-to-use devises and information and communication technologies in the present decade. In this review, two prospective plant diagnostic techniques that can be utilized for the SPA, and their applications in semi-commercial greenhouses, are introduced. The first technique is plant diagnosis based on a plant’s odor. Plants emit a broad range of volatile organic compounds and a plant’s emission profile changes depending on its physiological status. The second technique is chlorophyll fluorescence imaging. This technique measures the chlorophyll fluorescence induction phenomenon -a dynamic change in chlorophyll fluorescence intensity induced by illuminating a dark-adapted leaf with a stable intensity excitation light- and analyzes the shape of the induction curve. In addition, new challenges for an SPA-based mega-scale greenhouse are discussed.

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The aim of this study was to clarify optimal light quality conditions for maximizing the production of vindoline (VDL) and catharanthine (CAT) by Catharanthus roseus (L.) G. Don. in an enclosed artificial lighting plant factory. Both VDL and CAT are biosynthetic precursors of vinblastine (VBL), an anti-neoplastic agent. Since VDL and CAT occur at very low concentrations in C. roseus, the potential for increasing their production by manipulating lighting conditions is considered very important. In the first part of the experiment, we sought to identify which of the three horticultural cultivars tested (i.e. Kermesia, Dealbata and Titan) contained the highest concentrations of VDL and CAT. The Titan cultivar contained the highest CAT concentrations and had the highest seed germination rate. In the second part of the experiment, Titan was cultured hydroponically in an environmental room under a 16L/8D photoperiod and a total photosynthetic photon flux density (PPFD) of 150 μmol m^-2 s^-1 using four different lighting treatments; red light alone (R), blue light alone (B), a mixture of red and blue light (RB, R/B light PPFD ratio was 2:1), and white light from a fluorescent lamp (FL, control). A marked increase in plant growth parameters was observed in the R treatment, but no significant changes were observed in the VDL and CAT concentrations of whole leaves among the other light quality treatments. Although there were no significant differences in VDL and CAT yields, plants in the R treatment showed the highest mean concentrations of VDL and CAT among all treatments. In conclusion, irradiation with red light alone could be used to improve biomass production and yields of VDL and CAT in C. roseus, increasing the potential application of this plant species to the production of anti-cancer agents.

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We investigated how the supply of NO₃-N to triple-truss tomatoes grown for high soluble solids content (SSC) in a recirculating capillary hydroponic system affected growth, fruit yield, and SSC. Although decreasing the NO₃-N supply decreased the top fresh weight, top dry weight, leaf area, and fruit weight, SSC remained steady at > 9 % (Exp.1). Although leaf area was smaller in the S-M treatment (with a small amount of NO₃-N until flowering of the second truss then a medium amount) than in M-M (with a medium amount of NO₃-N before and after), the harvested fruits weight was almost equal, and SSC was > 10 % (Exp. 2). However, leaf area index (LAI) in S-L (with a small amount of NO₃-N then a large amount) was smaller than that in M-M, relative light intensity in S-L was greater than that in M-M and fruit weight (SSC > 8 %) in S-L was greater than that in M-M at a planting density > 5.7 m_-2 (Exp. 3). At LAI > 2.5, the increase in fruit weight per unit area tended to slow, although fruit weight per unit area in S-L was greater than that in the other treatments.
These results suggest that changing of the NO₃-N supply during the production of high SSC tomato improved fruit weight per unit area at high plant density.

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We investigated the effects of nightly duration of 4 months end-of-day (EOD) heating treatment in winter on flowering, yield and form of spray-type carnation (Dianthus caryophyllus L.) ‘ Light Pink Barbara’ and ‘ Cherry Tessino’ flowers. The minimum night temperature was raised to 17 ℃ for 0, 1, 3 or 5 h from 18:00. The number of days from pinching to flowering of ‘ Light Pink Barbara’, on shoots sprouted after the second pinching and on secondary lateral shoots decreased with longer heating. EOD heating for 5 h increased yields from January to March relative to no heating, and increased total yield. However, it decreased the length and weight of cut flowers and the number of florets. EOD heating for 3 h decreased days to flowering and increased the number of cut flowers while retaining the flower form of both cultivars in winter cultivation.

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