Phenotypic variations of maize after dry seed exposure to space conditions

--Pan, D, Zhou, W

It is known that space treated seeds usually show a pleiotropic effect on the phenotype of the plant during growth and development. The mechanism of the effect of space conditions on plant seeds is not really understood at the present time. In 2002, we sent seven maize inbred lines onboard the Space Shuttle Endeavor STS-112 to the International Space Station (ISS) for examination of the effect of space conditions on these inbred lines. After keeping the seeds on the ISS for ten days, the retrieved seeds were grown on earth and compared with Earth control seeds. Following is a summary of the observations on the phenotypes after germination and growth.

1. Generally, the inbred lines B73, W540 and A619 showed more vigor than their control counterparts during germination.
2. After space exposure, B73 had more tillers than control seeds.
3. One of the space treated inbred lines, A619, showed a mutagenic effect on the development of a purple strip on the shoot during growth.
4. On the ears of some of the space treated W540 inbred lines, the genetic effective kernels were found, and it was a lethal defect.
5. Space treated inbred line W22 r-r seeds showed early purple color intensified on the shoot during growth.
6. Space treated seeds of inbred-lines A619 and A631 showed earlier pollen shedding than Earth control seeds.

Generally speaking, some of the space treated seeds showed a variety of effects on phenotypes during germination and growth. The genetic consequence of the effect of space conditions on the seeds of some inbred lines is now under investigation.