The concentrated deep seawater, which is highly enriched in not only Na but useful minerals such as Mg, K and Ca is expected to be applicable to the production of high quality tomatoes. In the previous study, we reported that the short term salt stress treatment with the concentrated deep seawater can produce the high sugar tomatoes through osmoregulation in the phloem transport to fruits. In this study, the specificity of fruit quality of tomato grown with the concentrated deep seawater was examined with special reference to antioxidation, amino acid metabolism and sensory properties of fruits under the three different salt stress treatments. Tomato plants (Lycopersicon esculentum Mill.) were grown in hydroponic pots. In each of salt stress treatments, the concentrated deep seawater (DSW) or the surface seawater (SSW) or pure NaCl (NaCl) was applied to the nutrient solution for only two weeks at the stage of rapid fruit growth, where an electric conductivity of the nutrient solution was raised from 1.0 dSm^-1 to 15 dSm^-1. The two weeks salt stress treatment with the concentrated deep seawater brought high quality tomatoes with higher accumulations of sugar, acids, minerals of Mg and K, functional amino acids of γ-aminobutyric acid and proline and with good flavor. Furthermore, the activity of superoxide dismutase in DSW treatment was low as compared with that in SSW treatment and NaCl treatment. However, in this experiment, the significant differences in fruit quality (i.e. growth, contents of sugar, acid and functional amino acids) were not found among the three different salt stress treatments.

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Chlorophyll fluorescence imaging is a useful tool to assess photosynthetic ability of plant leaf without contact. By applying an actinic light of stable intensity to dark adapted leaf, a dynamic change in chlorophyll fluorescence intensity can be induced. This dynamic change in chlorophyll fluorescence intensity is called “Induction phenomenon”. “Induction method” is a representative way to detect photosynthetic dysfunction in plant leaf by analyzing the induction phenomenon. In this study, we investigated whether imaging of chlorophyll fluorescence induction phenomenon induced by weak actinic light at a PPFD of 10 μmol m^-2s^-1 can detect photoinhibition, which is caused by strong light irradiation treatments at PPFDs of 500, 1000 and 2000 μmol m^-2s^-1 for 1 hour. As a result, the photoinhibition in individual tomato leaves caused by the strong light irradiation treatments could be detected by measuring chlorophyll fluorescence induction phenomena that were induced by the weak actinic light. Furthermore, continuous measurement of chlorophyll fluorescence induction phenomena during a relaxation of photoinhibition under dark condition for 24 hours proved that P value, i.e. maximum chlorophyll fluorescence intensity in chlorophyll fluorescence induction phenomenon, can be used as an index of photoinhibition.

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In previous research, we have attempted to understand ecosystems thermodynamically from both experimental and theoretical perspectives by studying closed ecosystems, or microcosms, comprising chlorella, bacteria, and rotifers. We have obtained findings on the ecological structure (colony) and the thermodynamic stability and efficiency of the ecosystem. Many researchers have attempted to understand ecosystems from the viewpoint of thermodynamics, but the relationship between the characteristics of the organisms making up an ecosystem and the thermodynamic characteristics of that ecosystem remains unclear. In this study, we used microcosms to investigate changes in thermodynamic characteristics occurring when the characteristics of the organisms are changed. Specifically, we conducted experimental and theoretical examinations of changes in entropy production in the system in response to changes in the growth rate of rotifers, the consumer in the system. We obtained the following three findings: (1) Two entropy production areas exist when the growth rate of the consumer is increased, one in which production becomes higher and one in which it becomes lower, and a clear phase transition point is observed at the boundary between the two. (2) At this phase transition, the role of the consumer in the material circulation network changes qualitatively. (3) Entropy production of the entire system determines which of these two phases the system is directed toward, and organisms form interactive networks to reduce entropy production.

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We are planning to develop a new food production system utilizing Euglena gracilis, a photosynthetic microalga. In our previous reports, we investigated the influences of CO₂ concentrations (0.04 and 10%) and light qualities (red and blue) on its growth and nutrient contents. We found that the quantum yield of Euglena was greater than that of higher plants, and on 10% CO₂ condition and red and blue (PPFD ratio = 9:1) light irradiation was optimal for the growth and contents of protein and paramylon (β-1.3 glucan), and, in contrast, the 0.04% CO₂ condition and blue light irradiation was optimal regarding the contents of antioxidant vitamins. In this report, we investigated the qualities of these nutrients in Euglena compared with those in other algae (protein), yeast (vitamin). Euglena proteins were composed of large quantities of well-balanced essential amino acids, with a score of 88, and a high net protein utilization of 79.9, similar to cow-milk casein. Tryglycerides in Euglena were mainly composed of unsaturated fatty acids, especially linoleic and linolenic acids, which are essential fatty acids for humans, as well as a large amount of arachidonic acid. Euglena cells also contained higher levels of vitamins than yeast, a good vitamin source, and some minerals. Furthermore, Euglena cells accumulated paramylon. We thus concluded that Euglena cells were appropriate for use in new food source systems.

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