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Summary: To improve nutrient utilization and pathogenic resistance of plants in space, it is crucial to understand the effects of microgravity on the plant root microbiome. However, the finer details of whether and how microgravity affects the root microbiome remain unclear. Here, we found that simulated microgravity elicits no significant changes in fungal community composition and diversity, whether rhizosphere or endophytic. However, simulated microgravity caused a significant change in the composition and diversity of endophytic bacteria of wheat seedlings, but not in rhizosphere bacteria. The alteration of endophytic bacterial communities demonstrates that wheat seedlings adopt strategies to recruit additional endophytic Enterobacteriaceae and increase the stability of the endophytic bacterial network to respond to the challenge of simulated microgravity. Furthermore, our results also suggest that the corresponding changes in endophytic bacteria under simulated microgravity are closely related to a significant decrease in metabolites of the host's carbon metabolism, flavonoid biosynthesis, benzoxazinoid biosynthesis, and tryptophan metabolism pathways. Our findings reveal details important to our understanding of the impact of gravity on the microbial community of plant seedlings and the theoretical basis for manipulation of microorganisms to ensure efficient plant production in space. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Under normal gravity conditions, endophytic bacteria, one of the key bacterial community that inhabit in plant tissues, are well-known in promoting the plant growth and health, which are essential for long-term and long-distance manned microgravity space exploration. Here, we report how the Triticum aestivum endophytic bacterial communities behave differently under the simulated microgravity conditions. We demonstrate that, under simulated microgravity conditions, the microbial diversity in wheat seedling leaf increases while that in root decreases, compared to that cultivated under normal gravity conditions. We found that the dominant bacteria genus such as Pseudomonas , Paenibacillus and Bacillus significantly changes with gravity. The findings of this study provide important insight for space research, especially in terms of the Triticum aestivum cultivation in space. [ABSTRACT FROM AUTHOR]

As a consequence of the importance of crop cultivation in Bioregenerative Life Support System (BLSS), there is a necessity of protecting the plants from pathogenic diseases. Cave soil bacteria can be utilized as a source for isolating biocontrol bacteria that are suitable for plant growth in BLSS. Pseudochrobactrum kiredjianiae strain A4 (GenBank accession KT203923) is a gram-positive, short-rod shaped and whitish bacterium isolated from cave soil, and is culturable at 13 °C. A species-level identification was conducted by 16S rRNA gene sequencing, which showed that this strain had a 98% similarity with sequences of P. kiredjianiae isolated from the public domain. The A4 strain was positive for siderophore, indole-3-acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. The results of in vitro experiments showed that A4 could inhibit the growth and development of Rhizoctonia cerealis , Fusarium graminearumt , Magnaporthe grisea , Fusarium oxysporum and Botrytis cinerea . Under greenhouse conditions, the bacterium A4 improved the physiological parameters and reduced the defense enzymes activities of wheat ( Triticum aestivum L.) in the presence of R. cerealis . Statistical analysis of measured parameters revealed that A4-inoculated wheat plants were positively alleviating pathogenic stress. These results indicate that the isolate A4 provides a promising solution to control plant pathogenic fungi in BLSS. [ABSTRACT FROM AUTHOR]

Highlights: [•] 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. [Copyright &y& Elsevier]

Wheat ( Triticum aestivum L.) is one of the most important agricultural crops in both space such as Bioregenerative Life Support Systems (BLSS) and urban agriculture fields, and its cultivation is affected by several environmental factors. The objective of this study was to investigate the influences of different environmental conditions (BLSS, plant factory, green house and field) on the wheat growth, thousand kernel weight (TKW), harvest index (HI), biomass yield and quality during their life cycle. The results showed that plant height partially influenced by the interaction effects with environment, and this influence decreased gradually with the plant development. It was found that there was no significant difference between the BLSS and plant factory treatments on yields per square, but the yield of green house and field treatments were both lower. TKW and HI in BLSS and plant factory were larger than those in the green house and field. However, grain protein concentration can be inversely correlated with grain yield. Grain protein concentrations decreased under elevate CO 2 condition and the magnitude of the reductions depended on the prevailing environmental condition. Conditional interaction effects with environment also influenced the components of straw during the mature stage. It indicated that CO 2 enriched environment to some extent was better for inedible biomass degradation and had a significant effect on “source–sink flow” at grain filling stage, which was more beneficial to recycle substances in the processes of the environment regeneration. [ABSTRACT FROM AUTHOR]

Wheat ( Triticum aestivum L.) has been selected as one of the core crops in Bioregenerative Life Support Systems (BLSS) for future long-term space mission, and its cultivation is affected by several environmental factors. Both light system and nutrient solution are most efficient for plant growth. The objective of this study was to investigate the influences of different spectra combinations and ionic concentration (NH 4 + , K + , Mg 2+ , Ca 2+ , NO 3 − , H 2 PO 4 − , SO 4 2− ) on wheat growth, photosynthetic rate, transpiration rate, antioxidant capacity and biomass yield. The results showed that red–white light (RW) and white light (W) are more conducive to wheat growth and development. There are obvious advantages: photosynthetic rate, harvest index, thousand kernel weight, edible and inedible biomass. In order to conduct wheat cultivation for good quality, high yield and efficiency in the artificial environment, a valid state-space model of wheat growth process (WGP) was developed by experimental data and system identification, and then the inverse system model of WGP was derived accordingly to theoretically optimize the planting regime including light intensity and mineral ions concentrations based on prescribed output responses of WGP and computer simulation. Analysis of the most efficient nutrient mixtures showed that depending on the light (intensity and quality) and the plant age the different absorption of mineral elements from nutrient solution was observed. Therefore, it is important to develop a balanced nutrient mixture and light, which would provide the optimum uptake by plants of each element for the growing season. [ABSTRACT FROM AUTHOR]

There is much uncertainty about the risks of seed germination after repeated or protracted environmental low-dose ionizing radiation exposure. The purpose of this study is to explore the influence mechanism of low-dose ionizing radiation on wheat seed germination using a model linking physiological characteristics and developmental-dynamics simulation. A low-dose ionizing radiation environment simulator was built to investigate wheat ( Triticum aestivum L.) seeds germination process and then a kinetic model expressing the relationship between wheat seed germination dynamics and low-dose ionizing radiation intensity variations was developed by experimental data, plant physiology, relevant hypotheses and system dynamics, and sufficiently validated and accredited by computer simulation. Germination percentages were showing no differences in response to different dose rates. However, root and shoot lengths were reduced significantly. Plasma governing equations were set up and the finite element analysis demonstrated H 2 O, CO 2 , O 2 as well as the seed physiological responses to the low-dose ionizing radiation. The kinetic model was highly valid, and simultaneously the related influence mechanism of low-dose ionizing radiation on wheat seed germination proposed in the modeling process was also adequately verified. Collectively these data demonstrate that low-dose ionizing radiation has an important effect on absorbing water, consuming O 2 and releasing CO 2 , which means the risk for embryo and endosperm development was higher. [ABSTRACT FROM AUTHOR]

Energy consumption and output are two very important standards for evaluating the reliability of electric light sources when plants are grown in a controlled environment. As a primary source of energy, light is one of the most important environmental factors for wheat growth. The objective of this study was to investigate the influences of light/dark cycle operation with millisecond-scale period on the growth of wheat, photosynthetic characteristics, antioxidant capacity and biomass yield and quality during their life cycle. Four types of intermittent lighting with the same intensity were employed: a light/dark (0.5/0.5 ms) light (50%), a light/dark (0.7/0.3 ms) light (70%), a light/dark (0.8/0.2 ms) light (80%) and a continuous light (100%). The results showed that the wheat cultivated in the 80% light was characterized by highest photosynthetic rate and lowest lignin in inedible biomass, which was more beneficial to recycle substances in the processes of the environment regeneration. The data were comparable to those under continuous light condition in terms of chlorophyll concentration, antioxidant capacity, harvest index (HI) and thousand kernel weight (TKW). Wheat was sensitive to intermittent illumination which significantly affected those indices of growth and physiology, especially at heading and flowering stages. [ABSTRACT FROM AUTHOR]