Alexander A. Tikhomirov

Recycling efficiencies of C,H,O,N,S, and P elements in a biological life support system based on micro-organisms and higher plants

MELiSSA is a microorganism based artificial ecosystem conceived as a tool for understanding the behavior of ecosystems and developing the technology for future Manned Space Missions. MELiSSA is composed of four compartments colonized by the microorganisms required by the function of this ecosystem : breakdown of waste produced by men, regeneration of atmosphere and biosynthesis of edible biomass. This paper reports the mass balance description of a Biological Life Support System composed of the MELiSSA loop and of a Higher Plant Compartment working in parallel with the photosynthetic Spirulina compartment producing edible biomass. The recycling efficiencies of the system are determined and compared for various working conditions of the MELiSSA loop with or without the HPC.

Some Methods for Human Liquid and Solid Waste Utilization in Bioregenerative Life-Support Systems

Bioregenerative life-support systems (BLSS) are studied for developing the technology for a future biological life-support system for long-term manned space missions. Ways to utilize human liquid and solid wastes to increase the closure degree of BLSS were investigated. First, urine and faeces underwent oxidation by Kudenko’s physicochemical method. The products were then used for root nutrition of wheat grown by the soil-like substrate culture method. Two means of eliminating sodium chloride, introduced into the irrigation solution together with the products of urine oxidation, were investigated. The first was based on routine electrodialysis of irrigation water at the end of wheat vegetation. Dialysis eliminated about 50% of Na from the solution. This desalinization was performed for nine vegetations. The second method was new: after wheat cultivation, the irrigation solution and the solution obtained by washing the substrate containing mineral elements not absorbed by the plants were used to grow salt-tolerant Salicornia europaea L. plants (saltwort). The above-ground biomass of this plant can be used as a food, and roots can be added to the soil-like substrate. Four consecutive wheat and Salicornia vegetations were cultivated. As a result of this wheat and Salicornia cultivation process, the soil-like substrate salinization by NaCl were considerably decreased.

Optimal Structure of Plant Conveyor for Human Life Support in a Closed Ecosystem “Bios-3”

“Bios-3” experimental facility is designed to study different versions of closed ecological systems (CES) for human life support. Principal functions of regenerating environment for human in this facility are performed by a higher plant conveyor. The conveyor technique of plant cultivation is determined by the requirement of relative stability (in CES) of such conditions as CO2 concentration in the atmosphere, uniform time distribution of labor expenditures to till the plants, and uniform supply of food products reproduced by the plants. This is accomplished by endowing the plant conveyor with a certain age structure; its implementation and calculation technique is the subject of this report. The species structure of the plant conveyor in CES is a more complicated problem. The resolution of this problem is aimed to meet human food requirements by optimizing plant growing technologies suitable for CES. Issues for consideration include admissible level of vegetarianizing the human diet, traditional types of nutrition (European, Oriental, Northern, etc.), and the need and feasibility of correcting the ration by certain prestored components, etc. This paper considers several versions of multi-species conveyor structures implemented in 2–5 months-long experiments in “man higher plants” CES. These versions yielded fairly good results In supplying humans with oxygen, water and almost all vegetable products. These results suggest possible avenues to improve further the CES plant conveyor in accordance with chosen criteria for optimizing the human diet and plant growing technologies, primarily with the plant cultivation illumination mode.

Electrosynthesis of hydrogen peroxide from oxygen in a gas-diffusion electrode in solutions of mineralized exometabolites

The electrosynthesis of H2O2 in aqueous solutions (pH 1–9) of mineralized liquid and solid bio-wastes (exometabolites) for their processing in closed life-support systems was studied. It was shown that H2O2 can be obtained in these solutions by electrochemical reduction of oxygen in carbon black gas diffuse electrodes to concentrations of over 2 M with current efficiency 80%. The composition of the solution was found to affect the accumulation of H2O2 during the synthesis. The solutions can be concentrated further to 19 M H2O2. The results showed that the electrolytic method is promising for preparing H2O2 for closed life-support systems.

Light intensity and production parameters of phytocenoses cultivated on soil-like substrate under controled environment conditions

To increase the degree of closure of biological life support systems of a new generation, we used vermicomposting to involve inedible phytomass in the intra-system mass exchange. The resulting product was a soil-like substrate, which was quite suitable for growing plants (Manukovsky et al. 1996, 1997). However, the soil like substrate can be regarded as a candidate for inclusion in a system only after a comprehensive examination of its physical, chemical, and other characteristics. An important criterion is the ability of the soil-like substrate to supply the necessary mineral elements to the photosynthesizing component under the chosen cultivation conditions. Thus, the purpose of this work was to study the feasibility of enhancing the production activity of wheat and radish crops by varying the intensity of photosynthetically active radiation, without decreasing the harvest index. The increase of light intensity from 920 to 1150 μmol·m−2·s−1 decreased the intensity of apparent photosynthesis of the wheat crops and slightly increased the apparent photosynthesis of the radish crops The maximum total and grain productivity (kg/m−2) of the wheat crops was attained at the irradiance of 920 μmol·m−2·s−1. Light intensity of 1150 μmol·m−2·s−1 decreased the productivity of wheat plants and had no significant effect on the productivity of the radish crops (kg/m2) as compared to 920 μmol·m−2·s−1. The qualitative and quantitative composition of microflora of the watering solution and substrate was determined by the condition of plants, developmental phase and light intensity. By the end of wheat growth under 1150 μmol·m−2·s−1 the numbers of bacteria of the coliform family and phytopathogenic bacteria in the watering solution and substrate were an order of magnitude larger than under other illumination conditions. The obtained data suggest that the cultivation of plants in a life support system on soil-like substrate from composts has a number of advantages over the cultivation on neutral substrates, which require continual replenishment of the plant nutrient solution from the systems store to complement the macro- and micro-elements. Yet, a number of problems arise, including those related to the controlling of the production activity of the plants by the intensity of photosynthetically active radiation. It is essential to understand why the intensity of production processes is limited at higher irradiation levels and to overcome the factors responsible for this, so that the soil-like substrate could have an even better chance in the competition for the best plant cultivation technology to be used in biological life support systems.

Ontogenetic approach to assessment of chufa response to culture conditions by the method of chlorophyll fluorescence induction

Application of earlier proposed ontogenetic approach to assessment of chufa (Cyperus esculentus L.) response to artificial-light culture growing conditions differing in illuminance and type of mineral nutrition is described. It was shown that, on biological soil-like substrate, plant productivity did not increase as a result of PAR level rising, and life time of chufa leaves was reduced to 11 days as compared with 18 days on the neutral substrate. Changes in the parameters of chlorophyll fluorescence induction (Fv/Fm, Yield = (Fm − Ft)/Fm, and ETR = 0.5 × 0.84 × Yield × PAR) analyzed on the basis of ontogenetic approach show that it can disclose nonoptimal culture conditions.

TOLERANCE OF LSS PLANT COMPONENT TO ELEVATED TEMPERATURES

Stability of LSS based on biological regeneration of water, air and food subject to damaging factors is largely dependent on the behavior of the photosynthesizing component represented, mainly, by higher plants. The purpose of this study is to evaluate the tolerance of uneven-aged wheat and radish cenoses to temperature effects different in time and value. Estimation of thermal tolerance of plants demonstrated that exposure for 20 h to the temperature increasing to 45 degrees C brought about irreversible damage both in photosynthetic processes (up to 80% of initial value) and the processes of growth and development. Kinetics of visible photosynthesis during exposure to elevated temperatures can be used to evaluate critical exposure time within the range of which the damage of metabolic processes is reversible. With varying light intensity and air temperature it is possible to find a time period admissible for the plants to stay under adverse conditions without considerable damage of metabolic processes.

Volatile metabolites of higher plant crops as a photosynthesizing life support system component under temperature stress at different light intensities.

The effect of elevated temperatures of 35 and 45 degrees C (at the intensities of photosynthetically active radiation 322, 690 and 1104 micromoles m-2 s-1) on the photosynthesis, respiration, and qualitative and quantitative composition of the volatiles emitted by wheat (Triticum aestuvi L., cultivar 232) crops was investigated in growth chambers. Identification and quantification of more than 20 volatile compounds (terpenoids--alpha-pinene, delta 3 carene, limonene, benzene, alpha- and trans-caryophyllene, alpha- and gamma-terpinene, their derivatives, aromatic hydrocarbons, etc.) were conducted by gas chromatograph/mass spectrometry. Under light intensity of 1104 micromoles m-2 s-1 heat resistance of photosynthesis and respiration increased at 35 degrees C and decreased at 45 degrees C. The action of elevated temperatures brought about variations in the rate and direction of the synthesis of volatile metabolites. The emission of volatile compounds was the greatest under a reduced irradiation of 322 micromoles m-2 s-1 and the smallest under 1104 micromoles m-2 s-1 at 35 degrees C. During the repair period, the contents and proportions of volatile compounds were different from their initial values, too. The degree of disruption and the following recovery of the functional state depended on the light intensity during the exposure to elevated temperatures. The investigation of the atmosphere of the growth chamber without plants has revealed the substances that were definitely technogenic in origin: tetramethylurea, dimethylsulfide, dibutylsulfide, dibutylphthalate, and a number of components of furan and silane nature.

Spectral composition of light and plant productivity

Among other problems the Institute of Biophysics is working on the development of physiological and fundamental aspects of intensive light cultivation of higher plants. These technologies can be used in life support systems for stationary space station such as a Lunar base, a planetary base or a large orbital station. The source of energy may be the Sun or a nuclear reactor. In certain conditions, such sources of energy allow the use of a very broad range of irradiance of plants, in particular in the light energy range up to 2-3 times the solar energy (up to 100-1200 W/m2 PAR). Our Institute was the first to show that under such a high irradiance, some plants (radish, wheat, for example) can actively photosynthesize and exhibit high productivity on a sowing area basis. These results were later confirmed in the laboratory of Prof. Salisbury (USA).

The influence of leaf senescence on light dependence of chlorophyll fluorescence of radish leaves

15 Recording the chlorophyll fluorescence induction (ChFI), representing fast and slow changes in the chlorophyll fluorescence intensity occurring over time under continuous illumination of a photosynthesizing object after dark adaptation, is a promising and widely used method for studying photosynthesis in plants at different levels of organization of the photosynthetic apparatus [1, 2]. Despite the intensive studies and application of ChFI, the nature of its slow phase is not understood completely. This hampers a broader use of the method and limits its information capacity. An approach to elucidate the mechanisms of ChFI is to study lighttdependent process. In addition to the thee oretical aspect, this study has a practical significance because it allows a more correct selection of the illuu mination regime in biophysical, physiological, and ecological experiments. A large number of studies on the light dependence of ChFI have been carried out with isolated chloroplasts and algae [3–6]. Despite the fact that some studies on the light dependence of ChFI were performed with leaves of various plants [6–8], the transition to a more complex and heterogeneous syss tem, such as the leaf of higher plants, is associated with a number of features that should be taken into account so that the conclusions made in these studies are corr rect and unambiguous. Currently, the majority of studd ies in biophysics and ecology of plants by the ChFI method is performed with mature leaves, and the age of objects is estimated by the calendar method [6–9]. To characterize the functional activity of the phoo tosynthetic apparatus, the ratio of the fluorescence intensity at the maximum P (F P) to the steadyystate fluorescence level F S (F P /F S) is often used [1, 6, 10– 13]. This ChFI parameter is currently widely used in the physiological and ecological studies of plants to determine their tolerance [10, 11, 13]. It was estabb lished that, under longgterm exposure to a stressor, the F P /F S ratio is changed [1, 11–13]. Such a change in the fluorescence parameter is regarded as a criterion of disturbances in the electronntransport chain of photoo system 2 (PS 2) [1, 13]. However, it was shown that the F P /F S parameter also decreases in the course of leaf senescence [10–12]. It is known that the smallest changes in the F P /F S parameter of the leaf as well as in other important physiological and biochemical …