Carbon dioxide exchange of lettuce plants under hypobaric conditions.

Growth of plants in a Controlled Ecological Life Support System (CELSS) may involve the use of hypobaric pressures enabling lower mass requirements for atmospheres and possible enhancement of crop productivity. A controlled environment plant growth chamber with hypobaric capability designed and built at Ames Research Center was used to determine if reduced pressures influence the rates of photosynthesis (Ps) and dark respiration (DR) of hydroponically grown lettuce plants. The chamber, referred to as a plant volatiles chamber (PVC), has a growing area of about 0.2 m2, a total gas volume of about 0.7 m3, and a leak rate at 50 kPa of <0.1%/day. When the pressure in the chamber was reduced from ambient to 51 kPa, the rate of net Ps increased by 25% and the rate of DR decreased by 40%. The rate of Ps increased linearly with decreasing pressure. There was a greater effect of reduced pressure at 41 Pa CO2 than at 81 Pa CO2. This is consistent with reports showing greater inhibition of photorespiration (Pr) in reduced O2 at low CO2 concentrations. When the partial pressure of O2 was held constant but the total pressure was varied between 51 and 101 kPa, the rate of CO2 uptake was nearly constant, suggesting that low pressure enhancement of Ps may be mainly attributable to lowered partial pressure of O2 and the accompanying reduction in Pr. The effects of lowered partial pressure of O2 on Ps and DR could result in substantial increases in the rates of biomass production, enabling rapid throughput of crops or allowing flexibility in the use of mass and energy resources for a CELSS.     

Carbon dioxide exchange of lettuce plants under hypobaric conditions.

Growth of plants in a Controlled Ecological Life Support System (CELSS) may involve the use of hypobaric pressures enabling lower mass requirements for atmospheres and possible enhancement of crop productivity. A controlled environment plant growth chamber with hypobaric capability designed and built at Ames Research Center was used to determine if reduced pressures influence the rates of photosynthesis (Ps) and dark respiration (DR) of hydroponically grown lettuce plants. The chamber, referred to as a plant volatiles chamber (PVC), has a growing area of about 0.2 m2, a total gas volume of about 0.7 m3, and a leak rate at 50 kPa of <0.1%/day. When the pressure in the chamber was reduced from ambient to 51 kPa, the rate of net Ps increased by 25% and the rate of DR decreased by 40%. The rate of Ps increased linearly with decreasing pressure. There was a greater effect of reduced pressure at 41 Pa CO2 than at 81 Pa CO2. This is consistent with reports showing greater inhibition of photorespiration (Pr) in reduced O2 at low CO2 concentrations. When the partial pressure of O2 was held constant but the total pressure was varied between 51 and 101 kPa, the rate of CO2 uptake was nearly constant, suggesting that low pressure enhancement of Ps may be mainly attributable to lowered partial pressure of O2 and the accompanying reduction in Pr. The effects of lowered partial pressure of O2 on Ps and DR could result in substantial increases in the rates of biomass production, enabling rapid throughput of crops or allowing flexibility in the use of mass and energy resources for a CELSS.     

Plant growth and gas balance in a plant and mushroom cultivation system.

In order to obtain basic data for construction of a plant cultivation system incorporating a mushroom cultivation subsystem in the CELSS, plant growth and atmospheric CO2 balance in the system were investigated. The plant growth was promoted by a high level of CO2 which resulted from the respiration of the mushroom mycelium in the system. The atmospheric CO2 concentration inside the system changed significantly due to the slight change in the net photosynthetic rate of plants and/or the respiration rate of the mushroom when the plant cultivation system combined directly with the mushroom cultivation subsystem.     

Carbon dioxide interactions with irradiance and temperature in potatoes.

Separate controlled environment studies were conducted to determine the interaction of CO2 with irradiance and interaction of CO2 with temperature on growth of three potato cultivars. In the first study, an elevated CO2 concentration of 1000 micromoles mol-1 and an ambient CO2 of 350 micromoles mol-1 were maintained at the photosynthetic photon fluxes (PPF) of 17 and 34 mol m-2 d-1 with 12 h photoperiod, and at the PPF of 34 and 68 mol m-2 d-1 with 24 h photoperiod (400 and 800 micromoles m-2 s-1 PPF at each photoperiod). Tuber and total dry weights of 90-day old potatoes were significantly increased with CO2 enrichment, but the CO2 stimulation was less with higher PPF and longer photoperiod. Shoot dry weight was affected more by photoperiod than by PPF and CO2 concentrations. The elevated CO2 concentration increased leaf CO2 assimilation rates and decreased stomatal conductance with 12 h photoperiod, but had only a marginal effect with 24 h photoperiod. In the second study, four CO2 concentrations of 500, 1000, 1500 and 2000 micromoles mol-1 were combined with two air temperature regimes of 16 and 20 degrees C under a 12 h photoperiod. At harvest, 35 days after transplanting, tuber and total dry weights of potatoes reached a maximum with 1000 micromoles mol-1 CO2 at 16 degrees C, but continued to increase up to 2000 micromoles mol-1 CO2 at 20 degrees C. Plant growth was greater at 20 degrees C than at 16 degrees C under all CO2 concentrations. At 16 degrees C specific leaf weight increased substantially with increasing CO2 concentrations as compared to 500 micromoles mol-1 CO2, but increased only slightly at 20 degrees C. This suggests a carbohydrate build-up in the leaves at 16 degrees C temperature that reduces plant response to increased CO2 concentrations. The data in the two studies indicate that a PPF of 34 mol m-2 d-1, 20 degrees C temperature, and 1000-2000 micromoles mol-1 CO2 produces optimal tuber yield in potatoes.     

Measurements of trace contaminants in closed-type plant cultivation chambers.

Trace contaminants generated in closed facilities can cause abnormal plant growth. We present measurement data of trace contaminants released from soils, plants, and construction materials. We mainly used two closed chambers, a Closed-type Plant and Mushroom Cultivation Chamber (PMCC) and Closed-type Plant Cultivation Equipment (CPCE). Although trace gas budgets from soils obtained in this experiment are only one example, the results indicate that the budgets of trace gases, as well as CO2 and O2, change greatly with the degree of soil maturation and are dependent on the kind of substances in the soil. Both in the PMCC and in the CPCE, trace gases such as dioctyl phthalate (DOP), dibutyl phthalate (DBP), toluene and xylene were detected. These gases seemed to be released from various materials used in the construction of these chambers. The degree of increase in these trace gas levels was dependent on the relationship between chamber capacity and plant quantity. Results of trace gas measurement in the PMCC, in which lettuce and shiitake mushroom were cultivated, showed that ethylene was released both from lettuce and from the mushroom culture bed. The release rates were about 90 ng bed-1 h-1 for the shiitake mushroom culture bed (volume is 1700 cm3) and 4.1 approximately 17.3 ng dm-2 h-1 (leaf area basis) for lettuce. Higher ethylene release rates per plant and per unit leaf area were observed in mature plants than in young plants.     

Carbon balance and productivity of Lemna gibba, a candidate plant for CELSS.

The photosynthesis and productivity of Lemna gibba were studied with a view to its use in Controlled Ecological Life Support Systems (CELSS). Photosynthesis of L. gibba floating on the nutrient solution could be driven by light coming from either above or below. Light from below was about 75% as effective as from above when the stand was sparse, but much less so with dense stands. High rates of photosynthesis (ca. 800 nanomoles CO2 g dry weight (DW)-1 s-1) were measured at 750 micromoles m-2 s-1 PPF and 1500 micromoles mol-1 CO2. This was attained at densities up to 660 g fresh weight (FW) m-2 with young cultures. After a few days growth under these conditions, and at higher densities, the rate of photosynthesis dropped to less than 25% of the initial value. This drop was only partly alleviated by thinning the stand or by introducing a short dark period at high temperature (26 degrees C). Despite the drop in the rate of photosynthesis, maximum yields were obtained in batch cultures grown under continuous light, constant temperature and high [CO2]. Plant protein content was less than reported for field grown Lemna. When the plants were harvested daily, maintaining a stand density of 600 g FW m-2, yields of 18 g DW m-2 d-1 were obtained. The total dry weight of L. gibba included 40% soluble material (sugars and amino acids), 15% protein, 5% starch, 5% ash and 35% cellulose and other polymers. We conclude that a CELSS system could be designed around stacked, alternate layers of transparent Lemna trays and lamps. This would allow for 7 tiers per meter height. Based on present data from single layers, the yield of such a system is calculated to be 135 g DW m-3 d-1 of a 100% edible, protein-rich food.     

Measurement of rice crop metabolism using closed-type plant cultivation equipment.

In order to determine a required plant cultivation area which can sustain human life in a closed environment, the material circulating measurement system including a Closed-type Plant Cultivation Equipment (CPCE) in which the metabolic data of plants can be accurately measured has been constructed. According to results from cultivation experiments using rice, the harvest index was 29.9% for 110 days, and the required crop area to supply food, oxygen and water for one person was calculated to be about 111m2, 36m2 and 0.9m2, respectively.     

The Breadboard Project: a functioning CELSS plant growth system.

The primary objective of the Breadboard project for the next 3-4 years is to develop, integrate and operate a Controlled Ecological Life Support System (CELSS) at a one person scale. The focus of this project over the past two years has been the development of the plant growth facility, the first module of the CELSS. The other major modules, food preparation, biomass processing, and resource recovery, have been researched at the laboratory scale during the past two years and facilities are currently under construction to scale-up these modules to an operational state. This paper will outline the design requirements for the Biomass Production Chamber (BPC), the plant growth facility for the project, and the control and monitoring subsystems which operate the chamber and will present results from both engineering and biological tests of the facility. Three production evaluations of wheat, conducted in the BPC during the past year, will be described and the data generated from these tests discussed. Future plans for the BPC will be presented along with future goals for the project as the other modules become active.     

Trickle water and feeding system in plant culture and light-dark cycle effects on plant growth.

Rockwool, as an inert medium covered or bagged with polyethylene film, can be effectively used for plant culture in space station. The most important machine is the pump adjusting the dripping rate in the feeding system. Hydro-aeroponics may be adaptable to a space laboratory. The shortening of the light-dark cycles inhibits plant growth and induces an abnormal morphogenesis. A photoperiod of 12-hr-dark may be needed for plant growth.     

Effects of air velocity on photosynthesis of plant canopies under elevated CO2 levels in a plant culture system.

To obtain basic data for adequate air circulation for promoting plant growth in closed plant production modules in bioregenerative life support systems in space, effects of air velocities ranging from 0.1 to 0.8 m s-1 on photosynthesis in tomato seedlings canopies were investigated under atmospheric CO2 concentrations of 0.4 and 0.8 mmol mol-1. The canopy of tomato seedlings on a plug tray (0.4 x 0.4 m2) was set in a wind-tunnel-type chamber (0.6 x 0.4 x 0.3 m3) installed in a semi-closed-type assimilation chamber (0.9 x 0.5 x 0.4 m3). The net photosynthetic rate in the plant canopy was determined with the differences in CO2 concentrations between the inlet and outlet of the assimilation chamber multiplied by the volumetric air exchange rate of the chamber. Photosynthetic photon flux (PPF) on the plant canopy was kept at 0.25 mmol m-2 s-1, air temperature at 23 degrees C and relative humidity at 55%. The leaf area indices (LAIs) of the plant canopies were 0.6-2.5 and plant heights were 0.05-0.2 m. The net photosynthetic rate of the plant canopy increased with increasing air velocities inside plant canopies and saturated at 0.2 m s-1. The net photosynthetic rate at the air velocity of 0.4 m s-1 was 1.3 times that at 0.1 m s-1 under CO2 concentrations of 0.4 and 0.8 mmol mol-1. The net photosynthetic rate under CO2 concentrations of 0.8 mmol mol-1 was 1.2 times that under 0.4 mmol mol-1 at the air velocity ranging from 0.1 to 0.8 m s-1. The results confirmed the importance of controlling air movement for enhancing the canopy photosynthesis under an elevated CO2 level as well as under a normal CO2 level in the closed plant production modules.     

Biophysical effect of cosmic heavy ions of distinct LET-classes in a plant model system.

Results presented from recent space flight BION 9 show biological effects of different LET-classes of HZE-particles in different target regions of the seed (meristem and the whole embryo) of Arabidopsis thaliana (L.) Heyhn. HZE-one hit events and non-hit events, i.e. only hit by the low-LET background radiation, and their combined effects on the biological damage endpoint lethality are distinguished. This procedure is opening the opportunity of an approach to comparative studies of the biological effects induced by cosmic HZE-particles of different LET-ranges interacting in the complex cosmic radiation spectrum and with other space flight conditions.     

Carbon dioxide dynamics of combined crops of wheat,cowpea, pinto beans in the Laboratory Biosphere closed ecological system

A mixed crop consisting of cowpeas, pinto beans and Apogee ultra-dwarf wheat was grown in the Laboratory Biosphere, a 40 m³ closed life system equipped with 12,000 W of high pressure sodium lamps over planting beds with 5.37 m² of soil. Similar to earlier reported experiments, the concentration of carbon dioxide initially increased to 7860 ppm at 10 days after planting due to soil respiration plus CO₂ contributed from researchers breathing while in the chamber for brief periods before plant growth became substantial. Carbon dioxide concentrations then fell rapidly as plant growth increased up to 29 days after planting and subsequently was maintained mostly in the range of about 200–3000 ppm (with a few excursions) by CO₂ injections to feed plant growth. Numerous analyses of rate of change of CO₂ concentration at many different concentrations and at many different days after planting reveal a strong dependence of fixation rates on CO₂ concentration. In the middle period of growth (days 31–61), fixation rates doubled for CO₂ at 450 ppm compared to 270 ppm, doubled again at 1000 ppm and increased a further 50% at 2000 ppm. High productivity from these crops and the increase of fixation rates with elevated CO₂ concentration supports the concept that enhanced CO₂ can be a useful strategy for remote life support systems. The data suggests avenues of investigation to understand the response of plant communities to increasing CO₂ concentrations in the Earth’s atmosphere. Carbon balance accounting and evapotranspiration rates are included.     

Closed and continuous algae cultivation system for food production and gas exchange in CELSS.

In CELSS (Controlled Ecological Life Support System), utilization of photosynthetic algae is an effective means for obtaining food and oxygen at the same time. We have chosen Spirulina, a blue-green alga, and have studied possibilities of algae utilization. We have developed an advanced algae cultivation system, which is able to produce algae continuously in a closed condition. Major features of the new system are as follows. (1) In order to maintain homogeneous culture conditions, the cultivator was designed so as to cause a swirl on medium circulation. (2) Oxygen gas separation and carbon dioxide supply are conducted by a newly designed membrane module. (3) Algae mass and medium are separated by a specially designed harvester. (4) Cultivation conditions, such as pH, temperature, algae growth rate, light intensity and quantity of generated oxygen gas are controlled by a computer system and the data are automatically recorded. This equipment is a primary model for ground experiments in order to obtain some design data for space use. A feasibility of algae cultivation in a closed condition is discussed on the basis of data obtained by use of this new system.     

分子筛氧气浓缩器产氧性能实验分析

根据"变压-吸附-解吸附" 压力交变原理,研制了分子筛氧气浓缩器样机.通过不同入口压力、输出流量、高空压力和温度环境实验,测试了分子筛浓缩器样机的制氧性能.结果表明,分子筛氧气浓缩器样机产氧浓度随入口压力和上升高度的增加而增加;随输出流量的增加而减少;升降速度、环境温度影响不大.系统产氧性能基本满足系统工程生理学防护要求,其性能与国外产品有可比性.     

The effects of HGMFs on the plant gravisensing system.

High Gradient Magnetic Fields (HGMFs) offer new opportunities for studying the gravitropic system of plants. However, it is necessary to analyze the influence that HGMF can have on cellular processes and structures that may not be related to amyloplasts displacement. This paper considers possible HGMF effects on plants, which may accompany HGMF stimulation of amyloplasts and contribute to the mechanisms of the HGMF-induced curvature.     

Initial approach to comparative studies on the evolutionary potentials of space radiation effects in a plant system.

The role of cosmic ionizing radiation, including heavy ions (HZE-particles) in the induction of mutations at the molecule-, chromosome-, genome- and cell-level is discussed on the basis of different DNA organization in a pro- and eukaryotically compartmented plant system (Arabidopsis thaliana (L.) Heynh.). Data recently obtained on the biological effects of ionizing radiation make it timely to discuss comparatively the evolutionary potentials of space radiation effects in the pro- and eukaryotic genomes (plasmon, plastidom, chondriom, and nucleom) during long duration exposure on space flights.     

Use of sunlight for plant lighting in a bioregenerative life support system – Equivalent system mass calculations

Plant lighting is a critical issue for cost effectiveness of bioregenerative systems. A plant lighting system using sunlight has been investigated and compared to systems using electrical lighting. Co-generation of electricity and use of in situ resource utilization (ISRU) were also considered. The fixed part of equivalent system mass was found to be reduced by factors of from 3.1 to 3.9, according to the mission assumptions. The time-dependent part of equivalent system mass was reduced by a smaller value, of about 1.05. Cost effectiveness of bioregeneration has been compared to the cost of shipping food. Break-even times for different Lunar and Mars missions were generally in the order of 2–10 years, and were quite sensitive to the assumptions. There is significant scope for future refinement of these values, and work is ongoing.     

Effect of salt stress on growth and physiology in amaranth and lettuce: Implications for bioregenerative life support system

Growing plants can be used to clean waste water in bioregenerative life support system (BLSS). However, NaCl contained in the human urine always restricts plant growth and further reduces the degree of mass cycle closure of the system (i.e. salt stress). This work determined the effect of NaCl stress on physiological characteristics of plants for the life support system. Amaranth (Amaranthus tricolor L. var. Huahong) and leaf lettuce (Lactuca sativa L. var. Luoma) were cultivated at nutrient solutions with different NaCl contents (0, 1000, 5000 and 10,000 ppm, respectively) for 10 to 18 days after planted in the Controlled Ecological Life Support System Experimental Facility in China. Results showed that the two plants have different responses to the salt stress. The amaranth showed higher salt-tolerance with NaCl stress. If NaCl content in the solution is below 5000 ppm, the salt stress effect is insignificant on above-ground biomass output, leaf photosynthesis rate, Fv/Fm, photosynthesis pigment contents, activities of antioxidant enzymes, and inducing lipid peroxidation. On the other hand, the lettuce is sensitive to NaCl which significantly decreases those indices of growth and physiology. Notably, the lettuce remains high productivity of edible biomass in low NaCl stress, although its salt-tolerant limitation is lower than amaranth. Therefore, we recommended that amaranth could be cultivated under a higher NaCl stress condition (<5000 ppm) for NaCl recycle while lettuce should be under a lower NaCl stress (<1000 ppm) for water cleaning in future BLSS.     

Effect of CO2 levels on nutrient content of lettuce and radish.

Atmospheric carbon-dioxide enrichment is known to affect the yield of lettuce and radish grown in controlled environments, but little is known about CO2 enrichment effects on the chemical composition of lettuce and radish. These crops are useful model systems for a Controlled Ecological Life-Support System (CELSS), largely because of their relatively short production cycles. Lettuce (Lactuca sativa L.) cultivar 'Waldmann's Green' and radish (Raphanus sativus L.) cultivar 'Giant White Globe' were grown both in the field and in controlled environments, where hydroponic nutrient solution, light, and temperature were regulated, and where CO2 levels were controlled at 400, 1000, 5000, or 10,000 ppm. Plants were harvested at maturity, dried, and analyzed for proximate composition (protein, fat, ash, and carbohydrate), total nitrogen (N), nitrate N, free sugars, starch, total dietary fiber, and minerals. Total N, protein N, nonprotein N (NPN), and nitrate N generally increased for radish roots and lettuce leaves when grown under growth chamber conditions compared to field conditions. The nitrate-N level of lettuce leaves, as a percentage of total NPN, decreased with increasing levels of CO2 enrichment. The ash content of radish roots and of radish and lettuce leaves decreased with increasing levels of CO2 enrichment. The levels of certain minerals differed between field- and chamber-grown materials, including changes in the calcium (Ca) and phosphorus (P) contents of radish and lettuce leaves, resulting in reduced Ca/P ratio for chamber-grown materials. The free-sugar contents were similar between the field and chamber-grown lettuce leaves, but total dietary fiber content was much higher in the field-grown plant material. The starch content of growth-chamber lettuce increased with CO2 level.     

超临界二氧化碳闭式布莱顿循环系统研究进展

超临界二氧化碳(SCO₂)闭式布莱顿循环凭借高热效率、高紧凑性和高经济-环保性等优势,已成为能源与动力领域的热点技术之一。针对超临界二氧化碳闭式布莱顿循环,详细介绍了工作原理、优势及国内外相关研究进展,总结了循环总体热力、超临界工质叶轮机、紧凑高效换热器、控制及储热等相关关键技术的研究现状,并对当前工程应用面临的问题和未来技术发展方向进行了分析和展望。分析表明,循环总体热力设计阶段应涵盖部件低维性能分析,以评估部件性能指标的可实现性,并综合考虑全寿命周期性能、紧凑性、经济性等指标。工质的剧烈物性变化导致叶轮机与换热器内部特殊流动与换热机理,需发展充分考虑工质特殊物性影响的叶轮机和紧凑换热器设计方法;通过理论分析和机器深度学习相结合构建不同工质叶轮机相似方法,可为超临界二氧化碳叶轮机气动性能试验验证提供理论基础。此外,鲁棒高效的控制策略可实现超临界二氧化碳闭式布莱顿循环有效可靠调控,而集成新型介质储热技术的超临界二氧化碳闭式布莱顿循环系统将为高温光热发电提供关键技术支撑。