Annals of Botany

To boldly grow

In a recent book (Propitious esculent: the potato in world history. Heinemann, Oxford, 2008) John Reader suggests that in manned flights to Mars, the spacecraft should be able to accommodate a small stand of potatoes in order to feed the astronauts and to help maintain the CO2/O2 balance on board. However, if reliance is to be placed on plants grown in spacecraft then we need to know that plant growth and development are not unduly disrupted by the microgravity environment. Previous experiments to investigate plant growth in space have given conflicting results, as explained by De Micco et al. (Naples, Italy and Grenoble, France, pp. 661–669). In attempting to avoid some possible sources of variation, e.g. the intense gravitational changes that occur during re-entry, the authors set up an experiment in which soybean germination, seedling growth and then fixation of the seedlings after 5 d of growth were all performed automatically under microgravity during a 16-d orbit in the Foton-M2 capsule. After return to earth, seedlings were examined for general anatomical features and also by light, fluorescence and transmission electron microscopy. Particular attention was focused on the xylem and on the structure of xylem cell walls. Comparison was made with plants grown on earth but under otherwise identical conditions. Interestingly, growth under microgravity, albeit for only 5 d, had rather little effect on the seedlings. Clear effects were only seen at LM and EM levels: some xylem cell walls were thinner and there were perturbations in the orientation of cellulose microfibrils in the early stages of wall growth. However, this was not seen in the later stages of cellulose deposition when microfibrils assembled into normal lamellae. By the time secondary thickening occurred, xylem cell walls were similar (although sometimes thinner) to those in control plants. Returning to our opening theme, all this is good news for cosmic potato growers!