Will Plants Grow on Moon or Mars?

The cultivation of plants in space and on the Moon and Mars implies exposure to physical factors that are different from Earth: radiation, gravity levels and magnetic fields. As part of the MELiSSA (Micro-Ecological Life Support System Alternative) project where higher plants represent one of the compartments of an enclosed life support system, literature has been reviewed to assemble the relevant knowledge within space plant research. This review has particularly focused on the effect of the physical factors mentioned above on higher plant morphology, anatomy, gene regulation and genetic damage. Radiation studies on ground have shown increased damages to plant cells, and magnetic field studies have indicated some stress responses and altered growth rates, although not conclusive. Both in space and on ground (clinostat experiments) there are inconsistent results regarding gene expression and plant morphology. Anatomical flaws on the cellular level such as a reduced proliferation, displaced statoliths, ovoid chloroplasts, progressive vacuolization, and altered cell walls have been observed in several experiments. A normal plant reproduction process in weightlessness is feasible with a properly designed hardware. The same can be expected with low gravity levels, like those on Moon and Mars. In conclusion, the published results show that plants will grow and reproduce in low Earth orbit, but they might experience genotoxic stress and anatomic changes. Longer space studies, in particular outside the geomagnetic field and its radiation belt, are needed in order to investigate potential adaption responses since many studies show that plants can adapt in one generation to extreme environments.