Plants for Space Life: Testing the capacity of two edible species to cope with ionising radiation

The possibility of growing plants in Space is everyday more realistic. The cultivation of edible plants in Space is fundamental to minimize the need for food supplying from Earth and so to extend the duration of manned missions. One of the main constraints for plant cultivation in Space is ionizing radiation, which affects several growth processes, sometimes inducing positive outcomes at low doses. In this study, we compared the capacity to cope with radiation in two possible candidate species for Space farming: soybean (Glycine max L. Merr. ‘PR91M10’) and the mung bean (Vigna radiata L.). Both species were irradiated at the stage of seedlings with three different doses of X-rays (0.3, 10 and 20 Gy) and cultivated in a growth chamber under controlled environmental conditions. We focused our attention principally to young plants’ response at leaf level, both in terms of structure and function. More specifically, we investigated eco-physiological parameters and leaf functional anatomical traits linked with the photosynthetic efficiency. We also analyzed the content of pigments, proteins and antioxidant compounds. Results showed that both plant species exhibit an intrinsic radio-resistance at the highest dose of X-rays. In addition, the exposure of plants to low-doses promoted the synthesis of chlorophylls, carotenoids and membrane phenolics. The overall results confirmed that the positive outcomes of radiation are specie-specifics and dependent on the phenological stage. This should be taken into account in the choice of the species to be grown on board and in the design of cultivation chambers.