Résumé
Objective To study the stem development and essential oil distribution in different deve- lopment stages of Pogostemon cablin and to provide theoretical information and practical guidance for reasonable harvest and use of this medicinal plant. Methods Paraffin method, semi-thin sectioning, and histochemical method were used. Results Essential oil was not found in the promeristem of stem; in the primary meristem of stem and the early stage of stem's primary structure, the essential oil was mainly distributed in glandular hairs; in the primary structure of stem, the essential oil was mainly distributed in cortex parenchyma cells; in the secondary structure of stem, the essential oil was mainly distributed in remaining cortex parenchyma cell. Conclusion The essential oil is mainly distributed in the stem bark, so the thickness of a stem bark can be used as a standard of selective breeding index.