Comparative Anatomy Of Secretory Structures Of Six Species In Apocynaceae

Apocynaceae belongs to Eudicots,Asterids,Gentianales,one of the ten angiosperm families,including 5 subfamilies and 25 families.Apocynaceae plants are usually poisonous and have milk or water juice.At present,domestic and foreign researches on Apocynaceae mainly focus on chemical composition and pharmacology,but there is little research on anatomy of Apocynaceae and secretion structure of Apocynaceae.In this study,6 species of 3 subfamilies of Apocynaceae(Cynanchum thesiodes,Periploca sepium Bunge,Metaplexis japonica,Asclepias curassavica L.,Cynanchum chinense,and Catharanthus roseus)were used as the research objects.Using plant anatomy,semi-thin sectioning was used.The types,distribution and size of milk ducts in 6 plant vegetative organs were observed and studied.The aim is to provide a certain anatomical basis for the further study of the laticifer of the Apocynaceae family and the classification of the Apocynaceae family.The main findings are as follows:Microscopic observation of the leaves and stems of 6 species of Apocynaceae through plant anatomy revealed that the structures of the 6 species were in line with the typical characteristics of dicotyledons in general.The leaves are composed of epidermis,mesophyll,and veins.The leaves of the Cynanchum chinense are isobilateral leaf,and the leaves of the remaining 5 plants are dorsi-ventral leaf;the fence tissue of Metaplexis japonica mesophyll is composed of 2-3 layers of thin-walled cells,and the fence thin-walled cells of the remaining 4 plants are single-layered tight Induced columnar cells;the epidermis has stratum corneum,and only the lower epidermis has stomata,which is irregular;the vascular bundle is tough;all have laticifers.Transverse laticifer is generally located between mesophyll palisade tissue and sponge tissue,adjacent to vascular tissue.Except for Periploca sepium Bunge,the laticifer of the leaves of the other 5 plants are located near the midrib or lateral veins of the leaves,close to the vascular tissues.Among the vascular bundles of the laticifer leaves that are cut transversely by Periploca sepium Bunge leaves,the vascular bundles are located on both the proximal and distal axes of the vascular bundle.Articulated laticifers are found in Cynanchum thesiodes,Metaplexis japonica,Cynanchum chinense,and Catharanthus roseus.The laticifers of Cynanchum thesiodes and Catharanthus roseus are not branched.The laticifer of the other four plants have branched,and they have formed "Y" shaped laticifer.The structure of the stem includes three parts: epidermis,cortex and vascular column.Single-layer epidermis with cuticles;the surface of Periploca sepium Bunge is smooth without epidermal hairs,and the epidermis of the remaining5 species of plants has epidermal hair differentiation;Cynanchum thesiodes,Asclepias curassavica L.,and Cynanchum chinense bast are all distributed with bast fibers,and the remaining species No bast fibers;bast fibers of Cynanchum thesiodes and Asclepias curassavica L.tend to be lignified due to secondary growth,while Cynanchum chinense is not;in addition to Catharanthus roseus,the cortex,phloem and parenchyma cells of the remaining 5 plants Both contain starch granules;lysates of the parenchymal cells of Cynanchum thesiodes,Asclepias curassavica L.and Cynanchum chinense.Except for Catharanthus roseus,the stems of the five plants,Cynanchum thesiodes,Periploca sepium Bunge,Metaplexis japonica,Asclepias curassavica L.and Cynanchum chinense,all have laticifers.In these 5 plants,only the laticifers in Metaplexis japonica stems were distributed in two parts-the phloem and the pith,and the laticifers in the stems of the other four plants existed only in the pith.In these 5 plants,the laticifers of Periploca sepium Bunge and Cynanchum chinense are articulated laticifers;the laticifers in the sticks of Periploca sepium Bunge,Metaplexis japonica,and Asclepias curassavica L.,are non-articulated laticifers.Among them,the laticifers of Cynanchum thesiodes,Metaplexis japonica,Asclepias curassavica L.and Cynanchum chinense,were not branched,and only the laticifers of Periploca sepium Bunge were branched.The types of laticifer of Apocynaceae include both non-articulated laticifers and articulated laticifers.From an anatomical point of view,Asclepias curassavica L.laticifers are non-articulated laticifers,and the remaining 5 plants all have articulated laticifers.Asclepias curassavica L.has a long relationship with the other five plants;In the plants,the laticifers of Periploca sepium Bunge,Metaplexis japonica,Cynanchum chinense and Catharanthus roseus are all branched,and the relationship is closer.According to the BI tree,the genetic relationships among the three species,Metaplexis japonica,Cynanchum chinense and Asclepias curassavica L.were relatively close.The Metaplexis japonica and Cynanchum chinense are closer to each other.The relationship between the two species,Periploca sepium Bunge and Catharanthus roseus,is relatively close.According to the ML tree,the genetic relationship among the three species,Periploca sepium Bunge,Catharanthus roseus and Asclepias curassavica L.was found to be relatively close.Periploca sepium Bunge and Catharanthus roseus have a closer relationship.Metaplexis japonica has a long relationship with the other four plants.