In recent decades, the interest of the scientific community in plant space biology increased based on the certainty that cultivating higher plants in space is imperative for prolonged human missions. ...The cultivation of plants in space assumes great relevance moved by the consideration that there is a pivotal need to improve resource regeneration and onboard production of plant-based food, thus reducing the supply of resources from Earth. Therefore, the hereby paper provides an overview on the evolution of the interest in plant space biology from 2000 to 2023, basing the search on specific keyword combinations. The study encompasses (i) a proper quantitative search on the Scopus database; (ii) keyword frequencies and clustering analysis, (iii) a keyword network and time-gradient analysis and (iv) an elaboration of knowledge gaps comparing our results and recent reviews. Results highlighted an increase in publications in the last 10 years and a specific time-gradient related shifting on subtopics such as in situ resource utilization (ISRU) application and food production in a space mission context. Currently, knowledge gaps were identified in four research areas related to water dynamics in extra-terrestrial environments, plant physiology and biochemistry in response to growth on regolith, interactions with fertilizers, and plant/soil microbiome. Identifying these gaps will allow to canalize future efforts of space research where needed, facing the unsolved questions. Our analysis pointed out that space plant biology turned out to be oriented towards short and long-term space mission applications for improving resource regeneration and onboard/extraterrestrial-grounded production of plant-based food, thereby diminishing reliance on Earth for resupply.
•The scientific community's interest in plant space biology increased in the perspective of prolonged human missions.•The bibliometric analysis highlighted a general increase in publications in the last ten years.•Publications shifted their focus on subtopics such as ISRU application and food production in a space mission context.•Main identified knowledge gaps are water dynamics in space, plant growth on mars-like soils, and plant/soil microbiome.
Recently, cyanobacteria have gained attention in space exploration to support long-term crewed missions via Bioregenerative Life Support Systems. In this frame, cyanobacteria would provide biomass ...and profitable biomolecules through oxygenic photosynthesis, uptaking CO2, and releasing breathable O2. Their growth potential and organic matter production will depend on their ability to photoacclimate to different light intensities and spectra, maximizing incident light harvesting. Studying cyanobacteria responses to different light regimes will also benefit the broader field of astrobiology, providing data on the possibility of oxygenic photosynthetic life on planets orbiting stars with emission spectra different than the Sun. Here, we tested the acclimation and productivity of Synechococcus sp. PCC7335 (hereafter PCC7335), capable of Far-Red Light Photoacclimation (FaRLiP) and type III chromatic acclimation (CA3), in an anoxic, CO2-enriched atmosphere and under a spectrum simulating the low energetic light regime of an M-dwarf star, also comparable to a subsuperficial environment. When exposed to the light spectrum, with few photons in the visible (VIS) and rich in far-red (FR), PCC7335 did not activate FaRLiP but acclimated only via CA3, achieving a biomass productivity higher than expected, considering the low VIS light availability, and a higher production of phycocyanin, a valuable pigment, with respect to solar light. Its growth or physiological responses of PCC7335 were not affected by the anoxic atmosphere. In these conditions, PCC7335 efficiently produced O2 and scavenged CO2. Results highlight the photosynthetic plasticity of PCC7335, its suitability for astrobiotechnological applications, and the importance to investigate biodiversity of oxygenic photosynthesis for searching life beyond Earth.
•PCC7335 productivity under a low-visible high-far-red light spectrum is higher than expected.•PCC7335 doesn't activate FaRLiP under a low-visible high-far-red light spectrum, but acclimates trough type-III CA.•Production of phycocyanin can be boosted in PCC7335 with a far-red enriched spectrum.•The anoxic atmosphere enriched in CO2 does not affect cells' productivity nor physiological response.•PCC7335 can produce biomass, phycocyanin and modify an anoxic atmosphere with a low energetic demand.
The broad learning system (BLS) is an emerging approach for effective and efficient modeling of complex systems. The inputs are transferred and placed in the feature nodes, and then sent into the ...enhancement nodes for nonlinear transformation. The structure of a BLS can be extended in a wide sense. Incremental learning algorithms are designed for fast learning in broad expansion. Based on the typical BLSs, a novel recurrent BLS (RBLS) is proposed in this paper. The nodes in the enhancement units of the BLS are recurrently connected, for the purpose of capturing the dynamic characteristics of a time series. A sparse autoencoder is used to extract the features from the input instead of the randomly initialized weights. In this way, the RBLS retains the merit of fast computing and fits for processing sequential data. Motivated by the idea of "fine-tuning" in deep learning, the weights in the RBLS can be updated by conjugate gradient methods if the prediction errors are large. We exhibit the merits of our proposed model on several chaotic time series. Experimental results substantiate the effectiveness of the RBLS. For chaotic benchmark datasets, the RBLS achieves very small errors, and for the real-world dataset, the performance is satisfactory.
With long-term missions to Mars and beyond that would not allow resupply, a self-sustaining Bioregenerative Life Support System (BLSS) is essential. Algae are promising candidates for BLSS due to ...their completely edible biomass, fast growth rates and ease of handling. Extremophilic algae such as snow algae and halophilic algae may also be especially suited for a BLSS because of their ability to grow under extreme conditions. However, as indicated from over 50 prior space studies examining algal growth, little is known about the growth of algae at close to Mars-relevant pressures. Here, we explored the potential for five algae species to produce oxygen and food under low-pressure conditions relevant to Mars. These included
Chloromonas brevispina
,
Kremastochrysopsis austriaca
,
Dunaliella salina
,
Chlorella vulgaris
, and
Spirulina plantensis
. The cultures were grown in duplicate in a low-pressure growth chamber at 670 ± 20 mbar, 330 ± 20 mbar, 160 ± 20 mbar, and 80 ± 2.5 mbar pressures under continuous light exposure (62–70 μmol m
–2
s
–1
). The atmosphere was evacuated and purged with CO
2
after sampling each week. Growth experiments showed that
D. salina, C. brevispina
, and
C. vulgaris
were the best candidates to be used for BLSS at low pressure. The highest carrying capacities for each species under low pressure conditions were achieved by
D. salina
at 160 mbar (30.0 ± 4.6 × 10
5
cells/ml), followed by
C. brevispina
at 330 mbar (19.8 ± 0.9 × 10
5
cells/ml) and
C. vulgaris
at 160 mbar (13.0 ± 1.5 × 10
5
cells/ml).
C. brevispina, D. salina
, and
C. vulgaris
all also displayed substantial growth at the lowest tested pressure of 80 mbar reaching concentrations of 43.4 ± 2.5 × 10
4
, 15.8 ± 1.3 × 10
4
, and 57.1 ± 4.5 × 10
4
cells per ml, respectively. These results indicate that these species are promising candidates for the development of a Mars-based BLSS using low pressure (∼200–300 mbar) greenhouses and inflatable structures that have already been conceptualized and designed.
Human inhabitation of Space requires the efficient realisation of crop cultivation in bioregenerative life‐support systems (BLSS). It is well known that plants can grow under Space conditions; ...however, perturbations of many biological phenomena have been highlighted due to the effect of altered gravity and its possible interactions with other factors. The mechanisms priming plant responses to Space factors, as well as the consequences of such alterations on crop productivity, have not been completely elucidated. These perturbations can occur at different stages of plant life and are potentially responsible for failure of the completion of the seed‐to‐seed cycle. After brief consideration of the main constraints found in the most recent experiments aiming to produce seeds in Space, we focus on two developmental phases in which the plant life cycle can be interrupted more easily than in others also on Earth. The first regards seedling development and establishment; we discuss reasons for slow development at the seedling stage that often occurs under microgravity conditions and can reduce successful establishment. The second stage comprises gametogenesis and pollination; we focus on male gamete formation, also identifying potential constraints to subsequent fertilisation. We finally highlight how similar alterations at cytological level can not only be common to different processes occurring at different life stages, but can be primed by different stress factors; such alterations can be interpreted within the model of ‘stress‐induced morphogenic response’ (SIMR). We conclude by suggesting that a systematic analysis of all growth and reproductive phases during the plant life cycle is needed to optimise resource use in plant‐based BLSS.
The possibility of prolonging space missions—and consequently the permanence of humans in space—depends on the possibility of providing them with an adequate supply of fresh foods to meet their ...nutritional requirements. This would allow space travelers to mitigate health risks associated with exposure to space radiation, microgravity and psychological stress. In this review, we attempt to critically summarize existing studies with the aim of suggesting possible solutions to overcome the challenges to develop a bio-regenerative life support system (BLSS) that can contribute to life support, supplying food and O2, while removing CO2 on the International Space Station (ISS). We describe the physical constraints and energy requirements for ISS farming in relation to space and energy resources, the problems related to lighting systems and criteria for selecting plants suitable for farming in space and microgravity. Clearly, the dimensions of a growth hardware that can be placed on ISS do not allow to produce enough fresh food to supplement the stored, packaged diet of astronauts; however, experimentation on ISS is pivotal for implementing plant growth systems and paves the way for the next long-duration space missions, including those in cis-lunar space and to the lunar surface.
To conduct crewed simulation experiments of bioregenerative life support systems on the ground is a critical step for human life support in deep-space exploration. An artificial closed ecosystem ...named Lunar Palace 1 was built through integrating efficient higher plant cultivation, animal protein production, urine nitrogen recycling, and bioconversion of solid waste. Subsequently, a 105-day, multicrew, closed integrative bioregenerative life support systems experiment in Lunar Palace 1 was carried out from February through May 2014. The results show that environmental conditions as well as the gas balance between O
and CO
in the system were well maintained during the 105-day experiment. A total of 21 plant species in this system kept a harmonious coexistent relationship, and 20.5% nitrogen recovery from urine, 41% solid waste degradation, and a small amount of insect in situ production were achieved. During the 105-day experiment, oxygen and water were recycled, and 55% of the food was regenerated. Key Words: Bioregenerative life support systems (BLSS)-Space agriculture-Space life support-Waste recycle-Water recycle. Astrobiology 16, 925-936.
As we aim to expand human presence in space, we need to find viable approaches to achieve independence from terrestrial resources. Space biomining of the Moon, Mars and asteroids has been indicated ...as one of the promising approaches to achieve in-situ resource utilization by the main space agencies. Structural and expensive metals, essential mineral nutrients, water, oxygen and volatiles could be potentially extracted from extraterrestrial regolith and rocks using microbial-based biotechnologies. The use of bioleaching microorganisms could also be applied to space bioremediation, recycling of waste and to reinforce regenerative life support systems. However, the science around space biomining is still young. Relevant differences between terrestrial and extraterrestrial conditions exist, including the rock types and ores available for mining, and a direct application of established terrestrial biomining techniques may not be a possibility. It is, therefore, necessary to invest in terrestrial and space-based research of specific methods for space applications to learn the effects of space conditions on biomining and bioremediation, expand our knowledge on organotrophic and community-based bioleaching mechanisms, as well as on anaerobic biomining, and investigate the use of synthetic biology to overcome limitations posed by the space environments.
•Low-light treatment affects physiological and biochemical changes of wheat.•Low-light treatment at seedling stage has no significant effect on crop productivity.•Low-light treatment at grain filling ...stage affects final production significantly.
Minimizing energy consumption and maximizing crop productivity are major challenges to growing plants in Bioregenerative Life Support System (BLSS) for future long-term space mission. As a primary source of energy, light is one of the most important environmental factors for plant growth. The purpose of this study is to investigate the effects of low light intensity at different stages on growth, pigment composition, photosynthetic efficiency, biological production and antioxidant defence systems of wheat (Triticum aestivum L.) cultivars during ontogenesis. Experiments were divided into 3 intensity-controlled stages according to growth period (a total of 65days): seedling stage (first 20days), heading and flowering stage (middle 30days) and grain filling stage (last 15days). Initial light condition of the control was 420μmolm−2s−1 and the light intensity increased with the growth of wheat plants. The light intensities of group I and II at the first stage and the last stage were adjusted to the half level of the control respectively. For group III, the first and the last stage were both adjusted to half level of the control. During the middle 30days, all treatments were kept the same intensity. The results indicated that low-light treatment at seedling stage, biomass, nutritional contents, components of inedible biomass and healthy index (including peroxidase (POD) activity, malondialdehyde (MDA) and proline content) of wheat plants have no significant difference to the control. Furthermore, unit kilojoule yield of group I reached 0.591×10−3g/kJ and induced the highest energy efficiency. However, low-light treatment at grain filling stage affected the final production significantly.
As the core food crop of a bioregenerative life support system (BLSS), wheat is susceptible to pathogen infection due to the lack of effective microbial communities in the confined and isolated ...environment. Therefore, a thorough understanding of the dynamic changes in wheat rhizosphere fungi is of great significance for improving wheat production and ensuring the stability of the BLSS. In the current study, we collected samples of rhizosphere fungi in the four growth stages of wheat grown in the “Lunar Palace 365” experiment. We employed bioinformatics methods to analyze the samples’ species composition characteristics, community network characteristics, and FUNGuild function analysis. We found that the species composition of rhizosphere fungi in the wheat at the tillering stage changed greatly in the closed and isolated environment, while the species composition in the seedling, flowering, and mature stage were relatively stable. The results of the FUNGuild function analysis showed that the functions of rhizosphere fungi changed during wheat development. The rhizosphere fungal community was centered on
Ascomycota
,
Mortierellomycota
, and
Chytridiomycota
, and the community showed the characteristics of a “small world” arrangement. The stage of wheat seedlings is characterized by a greater abundance, diversity, and complexity of the network of interactions in the rhizosphere mycorrhiza community, while the tillering stage exhibited a greater clustering coefficient. Based on the changes in species composition, guild function regulation, and community structure differences of the wheat rhizosphere fungi in the BLSS, our study identified the critical fungal species during wheat development, providing a reference for ensuring the health and yield of plants in the BLSS system.
Key points
•
The diversity, composition, FUNguild, and network structure of rhizosphere fungi were analyzed.
•
Ascomycota, Mortierellomycota, and Chytridiomycota were the center of the rhizosphere fungal community network.
•
The effects of different wheat developmental stages on the community composition, function, and network structure of rhizosphere fungi were examined.
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