Micromorphology And Systematic Significance In Plagiogyriaceae,Dicksoniaceae And Cyatheaceae In China

Plagiogyriaceae is one of the key Family of Order Polypodiales.It mainly distributed in the tropical and subtropical regions of Asia.In the past studys,Plagiogyriaceae was considered have a closer genetic relationship with Osmundaceae.Therefore,Plagiogyriaceae is considered as a basal taxa of Polypodiales for a long time and it is the representative of Leptosporangiopsida.As studied by molecular systematics and reproductive biology showed that Plagiogyriaceae have a closer genetic relationship with tree ferns,in recent years.Plagiogyriaceae,Cibotium and Cyatheaceae is the mainly Tree ferns groups distributed in China region.In this paper,we use light microscope(LM)and scanning electron microscope(SEM)to compare the characteristics of palynology,leaf epidermis and transections of 21 species from Plagiogyriaceae,Dicksoniaceae and Cyatheaceae.To confirm whether the classification results from micromorphology are consistent with morphology and molecular systematics studys.To determine whether Micromorphology characters could be used as a basis for classification.To explore the evolution direction of micromorphology characters of Plagiogyriaceae,Dicksoniaceae and Cyatheaceae.The main research results are as follows:1.PalynologyWe observed spores of 20 species from Plagiogyriaceae,Dicksoniaceae and Cyatheaceae under SEM.The spores are radially symmetrical and trilete,The spores are often triangular in polar view,the three side is straight or concave,and flabellate or half round in equatorial view.The spores are trilete,the laesura arms are about1/2-2/3 length of the radius of spores.The mainly different between three Family is spore ornamentation types.The psilate,tuberculate,lophate and pterate and some transitional spore ornamentations types we presented here.The volume and ornamentation of spore could be used to differentiate the species in three family.2.Leaf epidermisWe observed leaf epidermis of 21 species from Plagiogyriaceae,Dicksoniaceae and Cyatheaceae under LM and SEM.Leaf epidermal cells were usually irregular in shape.The patterns of anticlinal walls was sinuate and sinuous.The stomatal apparatus were restricted in abaxial epidermis for all species,and generally could be assigned to Polocytic,Axillocytic,Coaxillocytic,Anomocytic and Desmocytic types.The length-width ratio of stomatal apparatus of Plagiogyriaceae and Dicksoniaceae is about 1,so the stomatal shape is near circular.The length-width ratio of stomatal apparatus of Cyatheaceae is about 2,so the stomatal shape is ellipse.The shape of cuticular layer mostly stripes and have little differences among three Family.Under SEM observation,the inner margin of the outer stomatal rim was offen sinuolate and smooth.The stomatal all showed Invagination type.The stomatal apparatus of leaf epidermis could be used to differentiate the species in three family.3.TransectionsWe observed transections of Pinnae of 18 species from Plagiogyriaceae,Dicksoniaceae and Cyatheaceae under LM.The results were as followed:The shape of the main vein of pinna are ususlly Inverted "U" type in adaxial;blunt process,"V" type,trapezoid type and Semicircle type in Abaxial.Transections of Pinnae consisted of Epidermis,Cortex,Parenchyma Sclerenchyma and vascular bundles.The main vein of pinna have 1-4 vascular bundle.The vascular bundle is amphicribral.The shape of Xylem mostly "?"type in Plagiogyriaceae,"V"type and "?" type often in other two Family.The vascular bundle number and Xylem shape of Pinnae could be used to differentiate the species in three Family.And thus also could be used for distinguishing different species in Cyatheaceae.According to the Palynology,Leaf epidermis and Transections of Pinnae,the Result show that 3 kinds of micromorphology all could be used to differentiate the species in three Family.Compare the micromorphology of three Family show that some characteristics of them have little difference,such as spore shape,leaf epidermal cell shape,guard cell shape,stomata shape,transection shape and structure of pinna,and vascular bundle type.Some characteristics have obviously difference,such as spore ornamentation types,stomatal apparatus and vascular bundle It turns out Dicksoniaceae and Cyatheaceae havea closer genetic relationhships among the three Family.In summary,micromorphology could not turn out Plagiogyriaceae,Dicksoniaceae and Cyatheaceae have a closer genetic relationhships as the result of Molecular phylogeny showed.