In order to investigate the genetic effect of space flight on pepper,the mutation on the root tip cells was studied in SP1 generation.The results showed that aerospace environment increased the mitotic index,and caused micronucleus and chromosomal aberrations including chromosome bridges,chromosome fragments and multipolar division etc.The rate of chromosome aberration and micronuclei were obviously increased in three treated materials compared with the untreated ones,which indicated that cytological mutations were induced by space flight.