Biometric anatomy of seedlings developed onboard of Foton-M2 in an automatic system supporting growth

During the evolution of higher plants on Earth, changes in numerous environmental factors occurred, but gravity has been a steady and unchanging force. The alteration of gravitational stimulus can cause modification of plant growth in various aspects that need to be investigated before the establishment of self-sustaining human colonies in Space, supported by bio-regenerative systems. This paper reports the results of an experiment conducted onboard of Foton-M2 satellite where soy seedlings grew during a 5-days period. The experiment was aimed to investigate the effect of microgravity on seed germination, seedling development, morphology and anatomy. The environmental conditions, other than gravity, of the ground control were repeated as identical as possible to those experienced on orbit. Seedlings developed in Space were compared with those grown in 1g1g on the basis of numerous anatomical and cytological parameters, such as size and shape of cells and intercellular spaces, amount and distribution of starch and phenolics in different organs and tissues. The observations made through light and fluorescence microscopy, together with the quantification of structural features, by means of digital image analysis, allowed to evidence that the various organs and tissues of soy seedlings show different degrees of alteration after the development in microgravity.