Abstract: [Objective] The secondary phloem from four species of three genera in the family Anacardiaceae (Rhus chinensis, Rhus potaninii, Pistacia chinensis, and Cotinus coggygria) were used to study the structural characteristics and patterns of distribution of various cells constituting the secondary phloem in different species. The structural characteristics of resin canals and their distribution were also clarified. This can provide a theoretical basis for studying the relationship between the development of plant secondary phloem, and the synthesis and structure of secondary metabolites,and to facilitate related evolutionary studies of Anacardiaceae plants.[Method] Bark samples were collected form Pistacia chinensis, Rhus potaninii, Cotinus coggygria and Rhus chinensis, the samples included vascular cambium, secondary phloem and periderm, but not secondary xylem. A comparative anatomical study of structural characteristics of the secondary phloem from four species in Anacardiaceae, and the composition and arrangement of its components in each, was meticulously conducted.[Result] The results showed that the secondary phloem of the four species in Anacardiaceae consisted of sieve tubes and companion cells, phloem parenchymal cells, phloem ray cells, resin canals and phloem fibres, which were arranged in a tangential band. However, some differences in the secondary phloem and resin canal structure among the four species were still observed. The conducting phloem and non-conducting phloem of the P. chinensis, R. potaninii and R. chinensis were clearly defined. Phloem ray cells in all species were arranged in a neat and vertical direction, except in R. potaninii, where they were obliquely distributed in the non-conducting phloem. The resin canal of R. potaninii was branched but not in the other three species, and only a small amount of fusion occurred between adjacent resin canals. There were a large number of phloem fibres in the secondary phloem of P. chinensis and C. coggygria, fewer in R. potaninii, and none in the phloem of R. chinensis.[Conclusion] The four Anacardiaceae species had noticeable differences in the secondary phloem cells and their resin canal structure. Rhus potaninii is the only species in Anacardiaceae found with branched resin canals, which provides a valuable basis for evolutionary studies of Anacardiaceae plants.

Key words: Anacardiaceae, Pistacia chinensis, Cotinus coggygria, Rhus potaninii, Rhus chinensis, secondary phloem, resin canal