The Research On Vegetative Organs Of Syringodium Isoetifolium And Zostera Marina

Paraffin section technology and optical microscope were used to observe the microstructure of the two seagrass's(Syringodium isoetifolium and Zostera marina)vegetative organs(leave,stem and root).By describing the structure characteristics of the two kinds of seaweed and compared their leave,stem and root with terrestrial plants respectively,the characteristics of them adapted to their submerged life in seawater were summed up.It can laid the foundation for further study on the mechanism of submerged life.In addition,it can offer a theoretical basis for the classification of seaweed and ecological restoration.Based on the paraffin section of vegetative organs(roots,stems and leaves)cross section,it can be observed that Syringodium isoetifolium and Zostera marina's roots were round,consisted of epidermis,cortex and vascular cylinder from the inside to the outside,the outside cell walls of Zostera marina endodermis were thickener than others;Both the two kinds of seaweed's stems are round,composed of epidermis,basic tissue,vascular tissue.Leave can be divided into three parts.They are epidermis,mesophyll and veins.In addition to the difference in morphological structure between the two kinds of seaweed,the differences in microscopic structure is mainly manifested in some point as mentioned below.Zostera marina leaves are long strips and Syringgodium isoetifolm leaves are circular.Compared with Syringodium isoetifolium,the length-width ratio of Zostera marina is smaller.The aerenchyma in Syringgodium isoetifolm leave is nearly circular,radially arranged around the center of the blade.While aerenchyma in Zostera marina appeared longer and arranged nearly in parallel along the long axis.Vascular tissue distributed two rounds in Syringgodium isoetifolm stem,esides a central vascular tissue in the center there are several peripheral vascular tissue in the outer ring.While in Zostera marina only center vascular existed in the center.In addition,there are several big and round airway distributed among the peripheral cell of Syringgodium isoetifolm,which is not observed in Zostera marina.The cross section Syringgodium isoetifolm appeared suborbicular and there were some cell residues.Cortex aerenchyma in each layer of cells arranged relatively scattered.Besides,no thickening observed in cortex.There are also similar cell residues appeared in Zostera marina and cortex aerenchyma cells arranged in a rule that each layer of cells are arranged in a ring.What's more,the lateral cortex cells'wall thickened obviously.The main characteristics adapted to submerged life is the following:there are a mass of developed aerenchyma appeared in the vegetative organs;there is no stomatal apparatus distributed in stem and leave;a large amount of chloroplasts contained in leaf epidermis calls;without or only very thin cuticle covered in leave;neither vascular tissue nor conducting tissue is not developed in leave,stem or root;the cell wall thickened in root endodermis.