[Comparative analysis of alfalfa seeds between space flight mutation and its control by Raman spectroscopy]

To realize the effect of space flight factors on chemical component of alfalfa seeds and its possible mechanism, seeds were loaded onto satellite "Jianbing No. 1" in 2006 for 14 days' space flight and then analyzed by Raman spectroscopy. Results showed that the intensity of two peaks (358 and 553 cm(-1)) of space flight seeds had been increased and the intensity of four peaks (814, 1 122, 1 531 and 1 743 cm(-1)) of space flight seeds had been decreased compared with its ground control. Based on the classification of Raman spectra, the increased peaks of 358 and 553 cm(-1) are related to DNA and Ca2+ respectively, which mean that the content of DNA and Ca2+ of alfalfa seeds had increased after space flight. The decreased peaks of 814, 1 122 and 1 743 cm(-1) are related to saccharide and fatty acid respectively, which mean that the content of reserve energy of alfalfa seeds had decreased after space flight. These findings can be explained as follows: (1) The increase in the content of DNA may be explained by the DNA damage induced by space flight factors and DNA syntheses and duplication before the cell division. (2) The increase in the content of Ca2+ may be stimulated by the complexity of gravity during the space flight, especially the hypergravity. Recent researches in Abrabidopsis thaliana have provided additional proof. (3) The decrease of the energy materials such as saccharide and fatty acid may be explained by the consumption both during the repair process of DNA damage induced by cosmic radiation and during the germination of seeds because the dormancy of alfalfa seeds had been broken up by space flight factors (cosmic radiation, microgravity, vibration or others) which subsequently resulted in that nutritious materials of alfalfa seeds were used earlier than its ground control.