Effect of spaceflight duration of subcellular morphologies and defense enzyme activities in earth-grown tomato seedlings propagated from space-flown seeds

Subcellular changes and enzymes activities were compared between Earth-grown plants from the original tomato seeds, 6-year long-term flown in the Mir Station and 27-day short-term flown in the satellite. In some first generation Mir-flown plants, the lamellae’s structure of some chloroplasts became curved and loose, and some mitochondrial outer membranes were broken. In some satellite-flown plants, the number of mitochondria increased, the lamellae’s structure of some chloroplasts became curved and loose, and some mitochondrial cristae disappeared. The number of starch grains per chloroplast in first generation, second generation, third generation Mir-flown plants and satellite-flown plants increased significantly compared with the ground control, but the difference between the number of starch grains per chloroplast in Mir-flown plants (include three generations) and satellite-flown plants was not significant. The number of chloroplasts per leaf cell in Mir-flown plants and satellite-flown plants increased significantly compared with the ground control. The activities of three defense enzymes supperoxide dismutase (SOD), peroxidase dismutase (POD) and catalase (CAT) in the satellite-flown plants increased significantly as compared with those of the ground controls and the Mir-flown plants, but the content of malondialdehyde (MDA) decreased significantly. Coefficients of variation of the activities of SOD, POD, CAT and the content of MDA in the satellite-flown plants were lest, and those in the Mir-flown plants were maximum. Coefficient of variation of the activities of SOD, POD, and CAT in the first, second and third generation Mir-flown plants were more than that in the ground control. The activities of defense enzyme in some Mir-flown plants increased significantly.