Abstract:After photoperiodic induction of Pharbits nil seedlings with two expanded cotyledons byshort day, the changes of protein in cotyledons or in shoot apex were investigated by polyacrylamide gel electrophoresis technique and electron, microscopy respectively Electron microscopicobservation shows that a kind of spherical electron-dense bodies appears in vacuoles of the apical meristem. Change of protein patterns also observed in the cotyledons. The number of basicprotein bands increased from eight in the untreated control to ten in the induced cotyledons, andthe number of, buffer-soluble protein bands increased from ten in the untreated control totwelve in the induced cotyledons. Authors suggest that the appearence of new protein bandsand electron-dense bodies is probably related to gene expression in the induction process ofphotoperiod of Pharbitis.