Pollen Morphologies Of Zygophyllaceae And Artemisia From The Middle And Western Regions Of Inner Mongolia

Pollen morphology is the basis of sporopollen analysis,and it is of great significance to explore the origin and differentiation of plants and identify and explain the strati-graphic fossil palynology.Zygophyllaceae is a group with many discrepancies in classical taxonomy,but there are few studies on its pollen morphology that reveal the differences between the genera in quantitative statistical analysis.Artemisia pollen is a common type of pollen in the stratum,and its pollen dominance usually were used to reflect open vegetation and arid climate.However,modern Artemisia has a wide distribution in arid and cold alpine meadows,semi-humid forest steppe and steppe,and warm and arid deserts and semi-deserts.Due to the similarities of pollen morphology,the Artemisia can only be differentiated to genus level,greatly hindered the use of its pollen to reconstruct vegetation and climate.Therefore,in this study we collected 6 genera,6 species of Zygophyllaceae,and 20 species of Artemisia in central and western Inner Mongolia plateau,and studied their pollen morphology under light microscope(LM)and scanning electron microscope(SEM).Furthermore,on basis of a series of measured indices and qualified indices,we used Classification and Regression Tree and Random Forest classification models to reveal the differences between pollen species(genus)from a numerical perspective of pollen morphology.The results are as follows:1)Zygophyllaceae pollen can be divided into 3 categories according to the four morphological characteristics of the aperture type,whether the operculum and membrane exists,nexine and sexine thickness ratio,and whether the colpus is shrinkage.Class ?: Pollen garin with pantoporate,and reticulate ornamentation,including T.terrestris;Class ?: Tricolporate type,including Peganum harmala L.and Nitraria tangutorum Bobr.The former has colpus membrane,porus operculum,and small reticulate ornamentation,and the latter has diamond porus,colpus membrane,and striate ornamentation.Class ?: tricolporoidate,small reticulate ornamentation type,including Zygophyllum mucronatum Maxim.,Tetraena mongolica Maxim.,and Sarcozygium xanthoxylum.The pollen of Z.mucronatum has shrinkage-colpus,and the thickness ratio of the nexine and sexine is greater than 2.The pollen of T.mongolica has normal colpus,and the thickness ratio of the nexine and sexine is greater than 2.The pollen of S.xanthoxylon has normal colpus,and the thickness ratio of the nexine and sexine is less than 2.2)According to the aperture type and exine ornamentation,20 species of Artemisia can be divided into 5 categories.Class I: The pollen with compound aperture,scaly spines ornamentation,including Artemisia anethoides and A.annua;Class ?: The pollen with compound aperture,and pyramid spines ornamentation,including A.anethifolia and A.ordosica;Class III: The pollen with compound aperture,and conical spines ornamentation,including A.frigida,A.blepharolepis,A.giraldii,A.princeps,A.scoparia,A.lavandulifolia,A.sylvatica,A.sieversiana,A.gmelinii and A.stechmanniana;Class ?: The pollen with simple aperture,non-conical spines,including A.dubia;Class ?: The pollen with simple aperture,conical spines ornamentation,including A.argyi,A.integrifolia,A.mongolica,A.sphaerocephala and A.tanacetifolia.This thesis includes the description of pollen morphology of 6 species of Zygophyllaceae and 20 species of Artemisia,pollen index table,and 193 photographs of light microscope and scanning electron microscope.