Pollen Morphology Of The Genus Epimedium (Berberidaceae) In China And Its Taxonomic Significance

Epimedium is a perennial herbaceous plant of Berberidaceae.It is a traditional and unique important medicinal plant in China.It has the effects of nourishing kidney,strengthening muscles and bones and removing rheumatism,and has outstanding effects in improving cardiovascular disease,improving immunity,preventing cancer,anti-cancer and anti-depression.According to the existing research statistics,there are about 68 species of Epimedium L.in the world,and 58 species are published in China.There are about 46 species after revision.About 85% of the taxa are uniquely distributed in China.Due to the rapid increase in the number of species in a short period of time,more than half of the species are published by foreign researchers based on a small number of cultivated individuals,and there is a lack of sufficient sample size.In addition,inter-species cross fertility leads to intricate relationships between species of the genus,which brings great difficulties and challenges to the taxonomic work of the genus.Pollen morphology is a stable inherited trait of plants and has important value for species of division and even phylogenetic reconstruction.A large number of studies have shown that using scanning electron microscopy to observe pollen morphology can provide useful help for plant identification and classification at the genus or specific level.In the existing pollen research of Epimedium L.,the research samples are often from wax leaf specimens,which may lead to the risk of pollen cross-contamination,and the research samples are often limited to a certain province’s origin or several species from different origins,while neglecting The concept of "population" has been introduced,but there is no comprehensive study on the pollen morphology of the entire genus.This study is based on the concept of "population".At the flowering stage,pollen morphology of the Epimedium L.plant cultivated in the homogenous garden was observed by scanning electron microscopy to explore the pollen morphology,variation patterns and taxonomic value.The relative species of E.sagittatum,E.acuminatum and E.chlorandrum,and the whole genus Epimedium L.has been comprehensively described and discussed.The pollen of the entire genus is systematically divided and the pollen morphology retrieval table is listed.The main research contents and conclusions are as follows: 1.A comparative study on pollen morphology of E.sagittatum and its sibling species,E.myrianthum having much in common with E.sagittatum.There are transitions in many morphological characters and even in key taxonomy features.In terms of geographical distribution,the two groups also have the same domain distribution.In the past,there were some descriptions of the pollen morphology of E.sagittatum in the research on the pollen of Epimedium L.,but there are few descriptions of the pollen morphology of E.myrianthum.Pollen size of E.sagittatum and E.myrianthum was(20.27 ~ 23.38)×(18.74 ~ 21.96)μm and(20.00 ~ 22.95)×(18.65 ~ 20.89)μm,respectively.The ornamentation of exine was an important character of pollen morphology.There were significant differences in ornamentation of exine among populations,which have been divided into three categories,namely reticulate,article reticulate and granular,and then divided into six subcategories according to the type of mesh ridge and mesh density.Among them,pollen morphology of E.sagittatum(including E.sagittatum var.glabratum)contained all three categories and six subcategories,and that of E.myrianthum contained three categories and four subcategories.This means that the pollen morphological variation pattern of E.myrianthum was a subset of E.sagittatum.On the whole,the variation pattern of the ornamentation of exine showed a trend,from reticulate to article reticulate,with the increase of latitude.And the main morphological characters of pollen were closely related to the elevation.As far as the pollen morphology concerned,the variation pattern of E.myrianthum was within the variation range of E.sagittatum,which was consistent with the variation patterns of other morphological characters.Pollen morphological characters could not distinguish the two taxa effectively,which failed to provide strong support for E.myrianthum as an independent species.It is suggested that the pollen morphological evidence is of relatively limited in clarifying the phylogenetic relationship among related taxa.However,further studies are still needed to provide strong evidence for the definition of large branches of phylogenetic trees of this genus.2.Study on pollen morphology of E.acuminatum.The pollen grain size of E.acuminatum is about(19.71 ~ 25.07)μm ×(20.34 ~ 24.31)μm.The pollen grain size of E.chlorandrum is about(21.41 ~ 22.44)μm ×(20.34 ~ 22.71)μm.There are large differences between different populations of E.acuminatum,and they can be divided into 2 major categories and 6 subcategories according to the decorative patterns of the outer wall of pollen.The pollen decoration on the outer wall of the two populations of E.chlorandrum is represented by 2 major categories and 2 subcategories.The pollen of E.chlorandrum is characterized by a subset of morphological variation of E.acuminatum.On the whole,the outer wall decoration type of E.acuminatum showed a trend of transition from mesh pattern to strip mesh pattern with the increase of latitude and altitude.The main morphological characteristics of pollen are closely related to altitude.In terms of pollen morphology and outer wall decoration features,the morphological variation of the three groups of E.acuminatum,E.chlorandrum,E.simplicifolium were all consistent with the direction of macroscopic morphological variation.Pollen morphology supported E.simplicifolium and E.chlorandrum was incorporated into E.acuminatum.3.Pollen morphology of the genus Epimedium(Berberidaceae)in China.In this paper,the pollen morphology of 90 species of 31 species of Epimedium L.is observed and studied by scanning electron microscopy.Among them,the pollen morphology of these six species was reported for the first time in the six species of E.brachyrrhizum,E.dolichostemon,E.epsteinii,E.qingchengshanense,E.rhizomatosum and E.ilicifolium.The results showed that the pollen morphology of Epimedium L.is single-grain pollen,nearly spherical,and the pollen size range is(17.85 ~ 25.09)μm ×(17.63 ~ 25.07)μm.According to the type of pollen outer wall,it can be divided into 3 basic types:(1)Reticulated,subdivided into 4 subtypes.(2)Article reticulate,subdivided into 4 subtypes.(3)Granular,In addition to E.sagittatum and E.myrianthum,other species also have a variety of pollen outer wall decorations,suggesting that the pollen morphology of the genus Epimedium L.may also have a wide range of variations.From the perspective of pollen morphology,the classification of this genus is discussed.Learning meaning requires more research on the population.