Study On Biological Effects Of Different Factors In Space Environment On Wheat

Seeds of different wheat genotypes were put in the centrifuge, lead screen container and the nuclear track detector aboard in the breeding satellite Shijian-8, which was launched on 9 September 2006. The effects of the space cosmic radiation, microgravity and their combination effect on wheat seedling growth, mitosis in the root tip cells, and the cytological effects of different water content in wheat seeds after space flight were studied in this paper with theγrays irradiation as a comparion .The results were as following:1. The wheat seedling growth was significantly inhibited in genotype Lunxuan 987 but no significant changes in Xinmai 18 and Zhoumai 18 induced by space radiation. Microgravity had no significant indirect effects on wheat seedling growth.2. Both cosmic radiation and microgravity in the space could induce significant chromosomal aberrations in the root tip cell, while the chromosomal aberration rate induced by space cosmic radiation was higher than that of microgravity. The chromosomal aberration rate induced by the combination of space radiation and microgravity was higher than that of any single factor of space environment, but lower than that ofγrays. The combination of space radiation and microgravity could induce higher circular chromosome thanγrays. The chromosomal aberration rate was higher in Xinmai 18 and Zhoumai 18 than in Lunxuan 987.3. Both cosmic radiation and microgravity could induce genetic mutation in wheat. The AFLP bands polymorphic frequencies increased in the seeds even not hit by space cosmic particles, and the polymorphic frequencies were 1.02% and 0.63% in Lunxuan 987 and Xinmai 18, respectively. The AFLP polymorphic frequencies in the seeds hit by space cosmic particles was higher than that of any single factor of space environment as well asγrays.4. Space environment inhibited the wheat seedling growth and mitosis of root tip cells in the seeds with 12% water content. The inhibited effect was reduced when the seed water content changed from 19% to 23%. The chromosomal aberration rate increased with the water content increasing.5. Space environment increased the chromosomal aberration rate of pollen mother cell in wheat. The aberration rate in wheat seeds with the water content of 19% was lower than that of 12%, and reached the highest when the water content was 23%, but deduced when the water content continued increasing.It could be concluded that both space radiation and microgravity could induce genetic mutation in wheat; Space radiation and microgravity had positive synergy effect for wheat mutation induction.