Serendipitous solution to the problem of culturing Arabidopsis plants in sealed containers for spaceflights of long duration.
For the development of an experiment to determine how a higher plant will develop from seed to maturity when deprived of essentially all gravitational information that it might use to guide its growth, we selected Arabidopsis thaliana as our test species. We were unable to culture it heterophically on nutrient agar in darkness. Light was required for germination and growth. Presumably the plants were dependent on photosynthesis for the major contribution to their organic nutrition. Plants were grown in relatively small modules closed to the atmosphere by plastic film. The permeability of the film for CO2 was found to be orders of magnitude too low for the plants to be growing by photosynthetic assimilation of CO2 diffusing into the modules from the ambient air. This anomaly was examined quantitatively. Rates of CO2 metabolism were measured for plants at various ages. The film permeability coefficient was rechecked. The effectiveness of the seal (as a barrier for H2O diffusion) and the dependence of diffusional transport on film thickness were reconfirmed. By elimination of all possible alternatives it was concluded that Arabidopsis thrives on light-assisted assimilation of organic compounds from the culture medium quite independently of a gaseous CO2 supply. Photoassimilation often has been reported for microalgae and photosynthetic bacteria but it is not commonly recognized that a higher plant can exhibit the same capability which greatly simplifies the establishment of reproducible culture conditions for test plants completely sealed from possibly noxious constituents of a spacecraft atmosphere or from the vacuum of free space. That Arabidopsis is a facultative photoheterotroph may be of even more general interest.
Brown
A H
AH
University of Pennsylvania, Philadelphia, PA 19104, USA.
O'Dowd
P
P
Loercher
L
L
Kuniewicz
R
R
Dahl
A O
AO
D017360:Arabidopsis / Q000254:growth & development* / Q000528:radiation effects; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism*; D003470:Culture Media; D003624:Darkness; D004780:Environment, Controlled; D008027:Light; D010100:Oxygen / Q000378:metabolism; D010539:Permeability; D010788:Photosynthesis; D018526:Plant Transpiration; D010969:Plastics / Q000737:chemistry; D012639:Seeds / Q000254:growth & development* / Q000528:radiation effects; D014867:Water / Q000378:metabolism
D003470:Culture Media; D010969:Plastics; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon; D010100:Oxygen