Effects of low nighttime air temperature (LNT) and high electrical conductivity (HEC) of a nutrient solution on the growth and yield of sweet pepper (Capsicum annuum L.) were investigated during winter (Oct 25, 2014 to Feb 28, 2015) in an experimental Venlo-type greenhouse in Kochi Prefecture. A “pre-night temperature drop,” which is a quick drop in the air temperature early in the nighttime, is often used in large-scale greenhouses. In this study, the length of the pre-night temperature drop was extended from 3 h (control) to 9 h (LNT), and the electrical conductivity of the nutrient solution supplied to the plants was increased from 2–3 dS m^-1 (control) to 3–4 dS m^-1 (HEC). The effects of LNT and HEC on the growth of sweet pepper differed between the periods before and after the winter solstice. Before the winter solstice, LNT significantly reduced the rates of stem elongation and node formation by 34% and 32%, respectively, whereas after the winter solstice, HEC became the key factor influencing the reduction in the rate of stem elongation, but neither LNT nor HEC affected the rate of node formation. Neither LNT nor HEC affected the leaf photosynthetic ability, or the number or dry weight of fruits, but HEC did reduce the total yield by inhibiting leaf expansion and fruit enlargement.

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Sensitivity analysis is an efficient way to characterize network systems such as metabolic reaction and closed ecological-life-support systems. This analysis can be performed efficiently using logarithmic gains, rate-constant sensitivities, and kinetic-order sensitivities defined in Biochemical systems theory (BST). In the present study, the steady-state sensitivities calculated by three calculation methods based on BST, i.e., S-system, GMA-system, and modified GMA-system methods, are compared to elucidate the performances of their methods and then to determine the best method for conducting correct sensitivity calculation. Comparisons clearly show that the modified GMA-system method always provides correct rate-constant and kinetic-order sensitivities, whereas the S-system and GMA-system methods give partially incorrect values because a flux in only one of the differential equations is partially differentiated despite the fact that the same flux is contained in different equations. It is demonstrated that the summation of the relevant sensitivities with respect to the same parameter in different differential equations provides correct values.

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A terrestrial cyanobacterium, Nostoc sp. HK-01 has several unique abilities: photosynthesis, nitrogen fixation and tolerance to space. The functions of Nostoc sp. HK-01 as a food resource in extraterrestrial environments such as Mars were investigated for future extraterrestrial agriculture, “Space Agriculture”. The nutritional energy of 100 g dry weight of Nostoc sp. HK-01 was estimated to be 358.1 ± 10.9 kcal by the results of protein, sugar and lipids. Six kind of recipes cooked using cyanobacteria were demonstrated and these results indicate that Nostoc sp. HK-01 has three food functions: primary (nutritional), secondary (sensory), tertiary (physiological). We will discuss the utilization of Nostoc sp. HK-01 as a food resource in closed bio-ecosystems. Our results may contribute to the supply of food resources under severe conditions for life-support in closed bio-ecosystems.

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