Yoshiaki Kitaya

Effects of CO2 enrichment and supporting materialin vitro on photoautotrophic growth ofEucalyptus plantletsin vitro andex vitro

SummaryEucalyptus camaldulensis shoots were cultured photoautotrophicallyin vitro for 6 wk with four different types of supporting materials (agar matrix, Gelrite matrix, plastic net, or vermiculite) under CO2-nonenriched or CO2-enriched conditions. Plantlets from each treatmentin vitro were then grownex vitro in a greenhouse for 4 wk. The growth and net photosynthetic rate of plantletsin vitro, as well as subsequent growth, survival percentage, transpiration rate, and net photosynthetic rate of plantletsex vitro were evaluated. CO2 enrichment significantly increased growth (total dry weight and number of primary roots) and net photosynthetic rate of plantletsin vitro, as well as the growth and survival percentage of plantletsex vitro regardless of the type of supporting materials. The growthin vitro was greatest in the vermiculite, followed by the plastic net, Gelrite matrix, and agar matrix (in descending order) under either the CO2-nonenriched or CO2-enriched conditions. The growth and survival percentage of plantletsex vitro were highest in the vermicultie under the CO2-enriched condition. The extensive root system producedin vitro was necessary for growth and survival of plantletsex vitro.

Iriomoteolide-3a, a Cytotoxic 15-Membered Macrolide from a Marine Dinoflagellate Amphidinium Species

A 15-membered macrolide, iriomoteolide-3a (1), with an allyl epoxide has been isolated from a marine benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was assigned by detailed analyses of 2D NMR data. Relative and absolute configurations were elucidated on the basis of conformational studies of 1 and its acetonide (2) and modified Moshers method of 1, respectively. Iriomoteolide-3a (1) and the acetonide (2) exhibited potently cytotoxic activity against antitumor cells.

Effects of light intensity and lighting direction on the photoautotrophic growth and morphology of potato plantlets in vitro

Abstract Photoautotrophic growth and morphological characteristics of potato (Solanum tuberosum L. cv. ‘Benimaru’) plantlets cultured in vitro with sideward lighting were compared with those cultured with conventional downward (overhead) lighting at four different photosynthetic photon flux densities (PPFDs) ranging between 30 and 120 μmol m−2 s−1. The shoot length was about 20 mm shorter in the sideward lighting treatment than in the downward lighting treatment at each PPFD. Dry weight, fresh weight and leaf area of the plantlets cultured in vitro photoautotrophically for 21 days in the sideward lighting treatment were similar to those in the downward lighting treatment at each PPFD. They increased with increasing PPFD to about 90 μmol m−2 s−1, then leveled off. The shoot length of the plantlets decreased with increasing PPFD in both lighting treatments. The sideward lighting system provided higher quality micropropagated transplants with reduced shoot length than the downward lighting system at each PPFD.

An overview of challenges in modeling heat and mass transfer for living on Mars.

Abstract:  Engineering a life‐support system for living on Mars requires the modeling of heat and mass transfer. This report describes the analysis of heat and mass transfer phenomena in a greenhouse dome, which is being designed as a pressurized life‐support system for agricultural production on Mars. In this Martian greenhouse, solar energy will be converted into chemical energy in plant biomass. Agricultural products will be harvested for food and plant cultivation, and waste materials will be processed in a composting microbial ecosystem. Transpired water from plants will be condensed and recycled. In our thermal design and analysis for the Martian greenhouse, we addressed the question of whether temperature and pressure would be maintained in the appropriate range for humans as well as plants. Energy flow and material circulation should be controlled to provide an artificial ecological system on Mars. In our analysis, we assumed that the greenhouse would be maintained at a subatmospheric pressure under 1/3‐G gravitational force with 1/2 solar light intensity on Earth. Convection of atmospheric gases will be induced inside the greenhouse, primarily by heating from sunlight. Microclimate (thermal and gas species structure) could be generated locally around plant bodies, which would affect gas transport. Potential effects of those environmental factors are discussed on the phenomena including plant growth and plant physiology and focusing on transport processes. Fire safety is a crucial issue and we evaluate its impact on the total gas pressure in the greenhouse dome.

The effect of gravity on surface temperature and net photosynthetic rate of plant leaves.

To clarify the effects of gravity on heat/gas exchange between plant leaves and the ambient air, the leaf temperatures and net photosynthetic rates of plant leaves were evaluated at 0.01, 1.0, 1.5 and 2.0 G of 20 seconds each during a parabolic airplane flight. Thermal images of leaves were captured using infrared thermography at an air temperature of 26 degrees C, a relative humidity of 15% and an irradiance of 260 W m-2. The net photosynthetic rates were determined by using a chamber method with an infrared gas analyzer at an air temperature of 20 degrees C, a relative humidity of 50% and a photosynthetic photon flux of 0.5 mmol m-2 s-1. The mean leaf temperature increased by 1 degree C and the net photosynthetic rate decreased by 13% with decreasing gravity levels from 1.0 to 0.01 G. The leaf temperature decreased by 0.5 degree C and the net photosynthetic rate increased by 7% with increasing gravity levels from 1.0 to 2.0 G. Heat/gas exchanges between leaves and the ambient air were more retarded at lower gravity levels. A restricted free air convection under microgravity conditions in space would limit plant growth by retarding heat and gas exchanges between leaves and the ambient air.

Effects of Air Current on Transpiration and Net Photosynthetic Rates of Plants in a Closed Plant Production System

The effects of the air current speed less than 1 m s-1 on transpiration (Tr) and net photosynthetic rates (Pn) of sweetpotato leaves and on a canopy of rice plants were determined using a chamber method and a combination of micro-meteorological and weighing methods, respectively. The effects of vertically downward moving and horizontal air currents on the Tr were also compared using a model plant canopy made from wet papers. The Tr and Pn of sweetpotato leaves were doubled as the air current speed increased from 0.01 to 0.3 m s-1 and was almost constant at air current speeds 0.3–1.0 m s-1. The Tr and Pn of the rice plant canopy increased linearly by 2.5 and 2 times, respectively, as the horizontal air current speed increased from 0.01 to 0.8 m s-1. Horizontal air current speeds above lms-1 are necessary to obtain maximal Tr and Pn of the canopy. The Tr of the model plant canopy was 2–3 times greater with the vertically downward air current than in the horizontal air current in an air current speed of 0.15–0.3 m s-1. A vertically downward air current at 0.3 m s” around leaves would be adequate for promoting Tr and Pn and thus plant growth in a closed plant production system.

Photoautotrophic growth of potato plantlets as affected by explant leaf area, fresh weight and stem length

Photoautotrophic growth in vitro of potato (Solanum tuberosum L. cv. Benimaru) explants varied with their initial leaf area and stem length. Photoautotrophic growth was much greater in leafy than in leafless explants. Variability in photoautotrophic growth was smallest in the explants with the greatest leaf area. The results indicated that use of explants with a large leaf area is important to maximize photoautotrophic growth and to minimize variation in photoautotrophic growth of explants in vitro.

Effects of air current speed on gas exchange in plant leaves and plant canopies

To obtain basic data on adequate air circulation to enhance plant growth in a closed plant culture system in a controlled ecological life support system (CELSS), an investigation was made of the effects of the air current speed ranging from 0.01 to 1.0 m s-1 on photosynthesis and transpiration in sweetpotato leaves and photosynthesis in tomato seedlings canopies. The gas exchange rates in leaves and canopies were determined by using a chamber method with an infrared gas analyzer. The net photosynthetic rate and the transpiration rate increased significantly as the air current speeds increased from 0.01 to 0.2 m s-1. The transpiration rate increased gradually at air current speeds ranging from 0.2 to 1.0 m s-1 while the net photosynthetic rate was almost constant at air current speeds ranging from 0.5 to 1.0 m s-1. The increase in the net photosynthetic and transpiration rates were strongly dependent on decreased boundary-layer resistances against gas diffusion. The net photosynthetic rate of the plant canopy was doubled by an increased air current speed from 0.1 to 1.0 m s-1 above the plant canopy. The results demonstrate the importance of air movement around plants for enhancing the gas exchange in the leaf, especially in plant canopies in the CELSS.

Development of a plant growth unit for growing plants over a long-term life cycle under microgravity conditions.

To study the effect of the space environment on plant growth including the reproductive growth and genetic aberration for a long-term plant life cycle, we have initiated development of a new type of facility for growing plants under microgravity conditions. The facility is constructed with subsystems for controlling environmental elements. In this paper, the concept of the facility design is outlined. Subsystems controlling air temperature, humidity, CO2 concentration, light and air circulation around plants and delivering recycled water and nutrients to roots are the major concerns. Plant experiments for developing the facility and future plant experiments with the completed facility are also overviewed. We intend to install this facility in the Japan Experiment Facility (JEM) boarded on the International Space Station.

Selection of microalgae suitable for culturing with digestate from methane fermentation

The effects of digestate on the growth rates of Euglena gracilis, Chlorella vulgaris, and Dunaliella tertiolecta were investigated to select suitable microalgae for culturing with digestate from methane fermentation. Microalgae were cultured in an aqueous solution containing digestate at concentrations of 5%, 10%, 13%, 20%, 40%, 50%, and 100%, and Cramer–Myers (CM) solution as a control, at photosynthetic photon flux densities (PPFDs) of 75–150 μmol m−2 s−1 with continuous illumination at 30°C. The number of cells was monitored daily, and specific growth rates (μ) were calculated as cellular multiplication rates. The maximum μ values of these species were greater in appropriate concentrations of digestate than in CM medium. The maximum μ values were 0.047 h−1 in 10% digestate for E. gracilis, 0.065 h−1 in 20% digestate for C. vulgaris, and 0.052 h−1 in 50% digestate for D. tertiolecta at a PPFD of 150 μmol m−2 s−1. The μ of D. tertiolecta were 2.5 and 1.1 times higher than those of E. gracilis and C. vulgaris, respectively, in 50% digestate. These results demonstrated that these species could be cultured at high growth rates with diluted methane fermentation sludge and that, among these species, Dunaliella sp. was suitable for culturing at higher concentration of digestate under relatively low-level light conditions.