Plant culture experiments in space require non-destructive and automated assessment of growth that is efficient and unattended. Currently, plant growth conditions in spacecraft are often captured by ordinary RGB (red, green blue) cameras. In addition to images in the RGB wavelengths, near-infrared (NIR) images that are not affected by plant pigments, such as chlorophylls, could be used to improve the quality of growth-related information. In this study, we examined the possibility of using NIR to assess the growth status of a model moss plant, Physcomitrium (Physcomitrella) patens. Mosses cultured in multi-well plates were imaged with a hyperspectral (HS) sensor, and the length of gametophores, the number of leaves and gametophores, and the amount of photosynthetic pigments in the moss colonies were measured. Then we used the R, G, B, and NIR (850 nm) bands from the obtained HS images to extract the moss colony areas and evaluate the amount of growth. Our results suggested that spectral indices using R and NIR bands were suitable for assessing the morphology of moss colonies and extracting the colony area. The extracted area can be used to estimate the amount of growth.

Bones are important organs for body resistance against force produced by gravity, though the influence of gravity on bone development is unclear. To examine the effects of gravity on osteogenesis, medaka larvae were reared in water or gel under various conditions. For determining the effects on bone development in a state of motion, larvae were reared in water under normal gravity (1g) or hypergravity (5g) conditions. Also, to examine the direct effect of gravity on bone mineralization, larvae were embedded in low melting agarose gel containing alizarin complexone (ALC) and reared for three days under a normal gravity (1g), simulated-microgravity (s-μg) with use of a clinostat device, or 5g condition. Medaka reared in water under the 5g condition showed forward protruding jaws and spreading of the mineralized area of jaw teeth as compared to those reared under the 1g control condition. In addition, the direction of growth of the notochord in the fin region was changed upward in those reared under the 5g condition, accompanied by a part of acetylated tubulin-positive nerves also localized upward, while positive signals for DsRed, expressed by an osterix promoter, in osteoblasts were increased in the fin region. On the other hand, in medaka reared in gel, ALC signals in the fin ray of those in the s-μg condition were increased as compared to those in the 5g condition. Changes noted in medaka larvae over three days indicated osteogenesis adaptation to the specific gravity environment. The present results obtained with an experimental system are considered useful for examinations in the future regarding changes of osteogenesis, which will be needed to clarify the mechanism of the effects of gravity on bone development.

To understand the combined effect of microgravity (μG) and space radiation on cells is an important requirement for the anticipated space travel by humans. Cultured cells, such as human fibroblasts and lymphoblasts, were used in previous studies, and we observed changes in the expression of some cell-cycle-related genes and increased chromosome aberrations (CAs) in these cells under simulated μG. In this study, we investigated the combined effect of μG and space radiation on human peripheral blood lymphocytes. Whole blood was irradiated with X-ray or carbon-ion (C-ion) beam while being exposed to simulated μG using a three- dimensional clinostat. The frequency of CA was assessed using the three-color fluorescence in situ hybridization on chromosome spreads of colcemid-induced prematurely condensed chromosomes in lymphocytes during the first cell division post irradiation. Compared with the cells irradiated at 1G, the frequency of CA was increased in cells simultaneously exposed to simulated μG and radiation even though cells were irradiated by the same doses (0.5–1.0 Gy). This result is similar to those of our previous studies in which we used human lymphoblast TK6 cells and human fibroblast 1BR-hTERT cells. These ground-based experiments give insights into the biological effects of the space environment where radiation and μG coexist.

This paper introduces the use of microarray data technology with the Agilent Maize Oligo Microarray (Design ID 016047) to characterize global changes in the transcript abundance of etiolated Zea mays (cv. Golden Cross Bantam) seedlings grown under microgravity (μg) conditions on the International Space Station (ISS) compared with those grown under 1 g conditions on Earth. Gene array data were analyzed according to stringent criteria that restricted the scored genes for specific hybridization values at least two fold. Of the 32152 - 32616 transcripts detected, 1030 and 590 transcripts were significantly different in the coleoptiles and in the mesocotyls. Of the transcripts detected, 877 and 428 transcripts were found to increase under μg conditions in the coleoptiles and the mesocotyls, respectively. Venn diagram analysis showed that 154 transcripts commonly increased and 10 decreased under μg conditions irrespective of the organ difference. Of these, phytohormone-related genes were focused, indicating that some of them were responsive to gravity. These results support the commonly accepted idea that phytohormone-related genes play a significant role in regulating plant growth and development under different gravity conditions.