ABSTRACT
This chapter provides an overview of the current knowledge about plant’s responses to altered gravity from molecular to the whole organism level. 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. Altered gravity produces changes in plant development, which are closely associated with modifications in the activities of meristems, specifically cell growth and cell proliferation/cell cycle. The accurate identification of stress factors, and the strategy followed by plants in their adaptation to an extra-terrestrial environment, will be necessary for achieving a successful cultivation of plants on board of spaceships and, in general, outside the Earth environment, which is essential to make manned space exploration possible. The current knowledge about the biological effects of radiation on photosynthetic organisms comes from experiments performed in long- and short-duration space missions.
