The effect of a synthetic cytokinin, 6-benzylaminopurine (BAP), on gene expression of RholPs in shoot apex segments of garden pea was examined by Northern blot hybridization using ^32P-labelled 560 bp partial RholPs cDNA fragment as the probe. The application of 10^(-12) M BAP, the lowest concentration tested, for 24h to the segments strongly activated the synthesis of RholPs transcripts as much as 7 times compared with those in BAP-untreated segments. In addition, the RholPs transcripts synthesis was enhanced by BAP in a concentration dependent manner, suggesting that BAP is concretely involved in the RholPs gene expression in the segments. A time course analysis of BAP on RholPs gene expression exhibited that BAP was closely related not only to the RholPs transcripts synthesis but also to the degradation of RholPs transcripts.