Growing plants under generated extra-terrestrial environments: effects of altered gravity and radiation

The coming enterprises of space exploration will surely require the cultivation of plants, not only as part of Bioregenerative Life Support Systems (BLSS), but also as a source of psychological well-being for space travelers. Considering that gravity plays a unique role in the configuration of a normal plant developmental pattern, only comparable with the effect of light, weightlessness is a major stress condition that should be fully understood. More than 50 years have passed since the first experiments performed in Space demonstrated that seed germination and plant growth can happen under conditions of altered gravity. Although with sometimes-contrasting results, data from experiments in real or simulated weightlessness indicate that microgravity itself does not prevent plant growth and reproduction; besides, the seed-to-seed cycle can be accomplished for several consecutive generations [1]. Indeed, during the evolution, being non-migrating organisms, plants have developed a high plasticity to adapt to changing environmental conditions. Such a high plasticity is the basis for coping with the limiting factors of extra-terrestrial environments. Morpho-functional changes due to microgravity at different plant levels have been attributed to the direct effect of microgravity on common metabolic pathways and on subcellular processes. Moreover, the interaction between microgravity and other factors,