Biological Characteristics And Systematic Significance Of Microlepia

Microlepia belongs to Dennstaedtiaceae which is one of the polypodiles groups of Polypodiales.There are about 50 species in China,mainly distributed in tropical and subtropical regions.The external morphology,spore morphology,petiole,vein and indusium of this genus are quite different from other genera.These morphological structures are often used as the basis for classification.At present,the classification of this genus has been controversial.In this study,Microlepia plants were systematically analyzed from morphology(coat condition),leaf epidermis micromorphology,palynology,gametophyte and cytotaxonomy,their systematic significance was discussed.Morphological characteristics: The hair covering and the edge shape of the terminal pinna of 21 species of Microlepia were analyzed and compared.The characteristics of 21 species of Microlepia are as follows: 4 kinds of coat conditions: long hair,long needle hair,short hair and no hair;Three kinds of pinna edge shapes: scalloped,serrated and lanceolate.Three kinds of pinna split: deep split,shallow split and no split.The sporangium mostly lives on the edge of the leaf and a few on the basal part of the notch.Indusium is cup-shaped and a few kidney-shaped.Morphological characteristics support the M.hookerian and M.speluncae in molecular systematics,but the M.strigosa and M.platyphylla in molecular systematics need further study.The morphological variation of M.marginata is quite large,which supports that M.marginata var.calvescens,M.marginata var.villosa and M.marginata var.bipinnata are variants of M.marginal.Leaf epidermal micromorphological characteristics: The leaf epidermal characteristics of 21 species of Microlepia were observed by light and electron microscopy.Under the light microscope,stomatal apparatus is only distributed in the lower epidermis and has an oval shape.The shape of the upper and lower epidermal cells is irregular,the vertical wall of the cells is sinuous and wavy.There are three types of stomatal apparatus: polar cell type,axillary cell type and irregular cell type.Under scanning electron microscope,the cuticular membrane of leaf epidermis is mostly ridge-shaped.Waxy ornamentation is mostly filamentous ornamentation.The outer arch cover of the air hole is smooth.The inner edge of the stomatal outer arch cover is nearly smooth and wavy.Both ends of guard cells arethickened with "T".Epidermal characteristics of interspecific leaves of Microlepia show certain differences which has certain taxonomic significance for species division.Palynology: Through scanning the spores of 21 species of Microlepia under electron microscope,the spore characteristics of Microlepia are as follows: tetrahedral,radiation symmetric;Polar view and equatorial view are nearly triangular and round triangular.It has three fissures,generally 1/3-2/3 of the total length of spores.Spore ornamentation is mainly reticulate ornamentation and hairy ornamentation.These characteristics show certain stability within the genus,indicating that Microlepia is a natural taxonomic group.Gametophyte: Gametophyte culture was carried out on five species of Microlepia.Spores germinated into the type of book fern,and the protophyllum developed into the type of Adiantum.The shape of the protophyllum was heart-shaped and did not have trichomes.The protophyllum showed primitive characteristics.The abdomen was densely populated with pseudoroots,hermaphrodite and attached to the abdomen of the protophyllum.Based on previous studies,the gametophyte characteristics of Microlepia are different from those of other genera,which can be used as the basis for classification.Research on cytotaxonomy: Chromosome numbers of five Microlepia species are as follows: M.marginata n=86,M.marginata var.villosa n=86,M.hancei n=86,M.spearucae n = 84,M.strigosa n=84,The chromosome base of Microlepia is x= 42,43.Among them,M.marginal is consistent with previous records,the chromosome numbers of the other 4 Microlepia species are reported for the first time.In summary,this paper provides reliable basic data for the systematic classification of species of Microlepia and related groups through experimental research.