Vessel Element Morphology Structure Of Woody Rosaceae In Northeast China

Rosaceae belongs to Rosales of Dicotyledonea.It is widely distributed in all provinces of China,with a total of 51 genera and more than 1000 species.There are altogether 32 genera,170 species,54 varieties and 15 forma in northeast China.There are 114 species of woody plants in 24 genera,32 varieties and 15 forma,thereinto 48 are cultivated species and 66 are wild species in northeast China.In this paper,Scanning electron microscope is used to comparative study in microstructural characteristics of vessel elements in 63 woody plants of 17 genera in Rosaceae in northeast China,the results are as follows:?.The average length of vessel molecules of Rosaceae woody plants in northeast China was between 161.17-480.20 ?m.The average diameter of catheter molecules ranged from 18.25 to 50.13 ?m.The average Angle of the end wall of the catheter was between 46.54-69.41°.The average tail length of the catheter molecule was between 19.77-59.90 ?m.The average volume of catheter molecules was between 6.04×104-5.28×105 ?m3.The following conclusions were drawn:However,its length,diameter,perforation plates area and other morphological characteristics will change.The rules are as follows:The molecular length of the catheter increases with altitude and latitude.The perforation plates area and diameter will decrease with the increase of altitude and latitude.By comparing the molecular volume of a single vessels in Rosaceae,the average molecular volume of a single vessel of the same species was not significantly different in different habitats,and the water demand of the same species was considered to be stable.Therefore,while maintaining the water diversion,the morphology will adapt to the change of habitat.?.In the measurement of vessel's tail length,it was found that the tail length of the same plant did not change much In different habitats,And the tail length had a certain relationship with the evolution of catheter molecules,and the longer the tail length was,the more primitive of the catheter molecules were.It was found that some species had functional structures at the tail end(with pits),and it was considered that the tail end of the vessels was involved in horizontal and vertical water transportation to varying degrees.?.There are four types of vessels: spiral?ladder?reticulate and pitted vessels.The pitted vessels are common in the Rosaceae.Ladder vessels have been observed only in the Spiraeoideae.There are two types of pits: opposite pitting?alternate pitting.And there are two types of pits in all 4 Subfamily,and there are a total of 10 species that only have alternate pitting.Two types of perforated plates were observed,namely scalariform perforated plate and single perforated plate.The Rosoideae were all single perforated plates.Scalariform perforated plate of Maloideae is less,only exists in the Sorbus pohuashanensis(Hance)Hedl.There are 8 species of plants with scalariform perforated plates in the Prunoideae and the Spiraeoideae.?.The molecular characteristics of catheter(types of perforation plate,types of pits,etc.of the same plants in different habitats did not change much,It is considered that these structural characteristics will not change with the change of habitat and that the molecular structure of the catheter has a certain taxonomic significance.Among them,the ladder duct was only found in the subfamily of hydrangea;in Maloideae,only the Malus,the Pyrus and the Sorbus have Reticulate vessels;in the Rosoideae,no ladder perforated plate was found;The feature of helical thickening does not exist in Rosoideae and Spiraeoideae,but in Prunoideae and Maloideae.It is believed that the helical thickening of inner wall thread can provide microscopic taxonomic support for the classification between Rosoideae.?.The degree of evolution of the subfamily of Rosaceae in Northeast China varies: By observed at perforation plate,types of pits,types of vessel and the structure of tail end of the vessels element,The Spiraeoideae contains most of the more primitive structural features(the ladder vessels,scalariform perforated plate and a longer tail end);However,there are a few species which have ladder perforated plate,but the total tail length of the vessel elements of Maloideae is longer than that of Prunoideae.Rosoideae found no scalariform perforated plate and ladder vessels,and the tail length is relatively short.It is generally believed that the evolution degree of vessel elements in the Spiraeoideae is not high.The evolution degree of vessel elements in the Maloideae was higher than that in the Spiraeoideae,and the evolution degree of vessel elements in the Prunoideae and Rosoideae was higher,but the evolution degree of vessel elements in the Rosoideae was higher than that in the Prunoideae.The observation and study on The level of molecular evolution of vessel elements in the Rosaceae suggest that the Rosaceae should be in a relatively early stage of evolution,that is,Although there is a relatively developed structure and features,but still remains a lot of original structure.?.By observing the arrangement of molecular grain holes in the ducts,it is found that there are many kinds of transverse connections of duct molecules in Rosaceae plants: there are two kinds of directly connected by ducts,or indirectly connected by wood fibers,tubular molecules,wood thin wall cells,etc.At the same time,it was found that the square arrangement of the catheter molecules was evidence of the connection between the catheter molecules and the wood thin wall cells.