Study of space environment on plant condition: Action of cosmic radiation

The space flights carried out so far have shown that living organisms are able, under certain relatively well-controlled conditions, to live for several months in space vehicles in low orbit. In the context of the space conquest to Mars, the duration of space flights will be extending between 2 and 3 years. In this frame, it is essential to design and set up a life support where plants have a crucial role as a source of food, in air renewal and in the recycling of waste.The two major challenges associated with space flight are radiation and microgravity effects on living organisms and, as the duration of space flights become longer, radiation doses and time of exposure to microgravity will become higher. It is therefore important to study the action of these factors on plant development.One of the characteristics of space radiation is the chronic exposure at low doses. The primary effect of low doses of radiation is a free radical formation and damage to DNA. Then, cells stop the cell cycle and initiate the mechanisms of DNA repairs. If the repair is incomplete, it can lead to mutations or cell death. Plants have an important post-embryonic development. Indeed, the growing apices of plants contain meristematic cells that continually produce tissues. These cells remain active throughout the plant's life and are particularly exposed to environmental factors that cause DNA damage and mutations.The impact of radiation exposure on plants may be described in terms of short-term effects and long-term risks. Here, we studied the short-term adaptation of plants to radiation during its early vegetative development. Plants of Arabidopsis thaliana have been exposed to low dose of chronic radiation (0.4 mGy/day) and to simulated microgravity (10-4g) using a Random Positioning Machine (RPM). A morphometric analyze, a study of oxidative stress and a characterization of cell cycle have been carried out on root apices of seedlings exposed during 6 days to radiation and / or simulated microgravity. Space is a complex and new environment to which plants must adapt. This study contributes to a better understanding of the effects of the short-term space environment on vegetative development of plants, as well as the interplay between radiation and microgravity on the adaptation of plants to this new environment.