The objective of our research on Petunia hybrida is to understand the role of calreticulin in the growth of pollen tubes in the pistil. The aim of this study was the first step: finding out whether CRT gene expression takes place in unpollinated and pollinated styles. It was revealed by in situ hybridization that the transcription of the calreticulin gene takes place in the transmitting cells of unpollinated and pollinated styles and in pollen tubes growing in vivo. The mRNA transcripts of the CRT gene were localized mainly on the surface of endoplasmic reticulum (ER) membranes, both in transmitting cells and in the tip cytoplasm of pollen tubes. The results of this study show that calreticulin can be involved in pollen ? pistil interaction in vivo.