Study On The Evolutionary Structure Of Philadelphus Pekinensis Rupr.in Different Ecological Environments

In this paper,by combining the technique of paraffin section,leaf epidermis of production technique,freehand section technique,dispersing of vessel elements technique,optical photomicrography technique and mathematical statistic analysis technique,to have a comparative study on the system evolution structure of Philadelphus pekinensis Rupr.which are lived in different ecological environment: shade and sun ecological environment,and collection of medicinal,ornamental and beautify the urban value in one body,have a synchronous structure comparative study on the leaves,petioles,young stem and secondary xylem,timber catheter of P.pekinensis Rupr.lived in shade and sun environment resistance to shade environment and arid environment,the experimental results show that:1.The P.pekinensis Rupr.lived in shade environment have large and thin leaves,sparse veins,larger epidermal cells,there is no stomata on the upper epidermis,lower epidermal cells without cuticula,the number of stomata is small and the aperture is large,the results show that the P.pekinensis Rupr.evolved out of a special apparent structure to antagonistic shade environment.The P.pekinensis Rupr.lived in sun environment have small and thick leaves,dense veins,smaller epidermal cells,and the cells arranged closely,there is also no stomata on the upper epidermis,the cuticula of the lower epidermal cells showed radiation thickening,the number of stomata is large and the aperture is small,usually have sunken stomata,this structure can refract hard light,to avoid burns,thereby effectively antagonistic arid environment stress.2.In the shade environment,the number of heterocyst in the leaf epidermis cells is more;the cuticula is thin,leaf palisade tissue structure is degraded,the quantity is small and the structure is loose,palisade tissue/spongy tissue have a small ratio,the aeration tissue is developed,vein vascular tissue have a simple structure.There are more heterocyst cells in the epidermal cells of petiole,less collenchymas;the number of clusters is small,the xylem catheters of vascular bundle have a small quantity and loose arrangement,the bundle sheath composed of parenchyma cells without corner thickening composition.Young stems nearly round,larger in diameter;the cuticula is thin,less collenchyma in cortex,phloem fiber is not developed,the vascular bundle type of stem is collateral bundle.Synchronous experimental results are demonstrated that the cuticle of leaf epidermis cells is thicker in sun environment,leaf palisade tissue structure is developed,the quantity is many and the arrangement is close,palisade tissue/spongy tissue have a large ratio,vein vascular tissue have a developed structure.There are less heterocyst cells in the epidermal cells of petiole,developed collenchymas,the number of cell layer and clusters is large,the xylem catheters of vascular bundle have a large quantity and closely arranged,the bundle sheath composed of small cells with angular collenchymas.Young stems with hexagonal shape,smaller in diameter,the cuticula is thick,more collenchyma in cortex,phloem fiber is developed,the vascular bundle type evolved into bicollateral vascular bundle.3.The experimental results of three sections of wood show that: the diameter of the catheter is smaller and the quantity is less in the transverse section of the P.pekinensis Rupr.wood which lived in shade environment,in the tangential section,the ray cells are small and the ray width is narrow,the length and width of upright cells,procumbent cells in radial section are smaller.The diameter of the catheter is larger and the quantity is more in the transverse section of the P.pekinensis Rupr.wood which lived in sun environment,in the tangential section,the ray cells are big and the ray width is wide,the length and width of upright cells,procumbent cells in radial section are biger.4.The results of segregation of wood show that: the average of catheter length and width are small in P.pekinensis Rupr.fiberize which lived in shade environment.The average of catheter length and width are large in P.pekinensis Rupr.fiberize which lived in sun environment.To sum up,P.pekinensis Rupr.in two kinds of environment antagonism of adversity evolved different structure to adapt to its environment.The research results show the ecological environment directly affects the construction of plant structure.This paper provides the theoretical reference and the first evolutionary structural evidence for the identification,selection,cultivation and planting of P.pekinensis Rupr.It has laid an important theoretical foundation for the further research of the following stress resistance of P.pekinensis Rupr..