Abstract: The expression patterns of a maize calmodulin kinase (CaM kinase,CaMK) by immunohistochemical localization were studied. The results indicated that while the CaMK was widely distributed in maize,from vegetative to reproductive organs,its expression was highly re-(gulated) spatially and temporally.CaMK was mainly accumulated in vascular bundle sheath cells of leaves and highly expressed in lateral root primordia and root tips.But the kinase was under detectable in other regions.In reproductive organs,much CaMK was found in young embryos and some anther cells such as microspore mother cells,tetrads and tapetum.In mature embryo sacs,significant amounts of CaM kinase was also observed in the egg cell,central cell and at the interface of these two cells.All these findings provided clues for biological functions of thes CaM kinase in maize.