Morphological And Systematic Studies Of Asteraceae Taxa Of Four Subfamilies In Northeast China

The morphological structures(especially the micro-morphological structures)of the leaf,cypsela and seed of 173 taxa(169 species,2 varieties and 2 forms)representing 68 genera from 4 subfamilies of Asteraceae in Northeast China were deeply studied in this research,using morphological observation,glycol methacrylate(GMA)sections,phylogenetic analysis and molecular systematic method.In addition,ITS(Internal Transcribed Spacer)sequence of some species were studied.The phylogenetic trees of Asteraceae in Northeast China were constructed based on the morphological characteristics and ITS sequences of the species used in this study.The study showed that the species used for this study of Asteraceae in Northeast China were included in four subfamilis Mutisioideae,Carduoideae,Pertyoideae and Asteroideae,respectively.Mutisioideae.The subfamily includes two clades: Adenocaulon and Leibnitzia.Adenocaulon has no pappus on the apical part of the cypsela.The glandular trichomes with multicellular stalk and head cover on the cypsela of the genus Adenocaulon.The mesocarp is composed of parenchyma cells with druse.The outermost layer of the testa is sclereid and the vascular bundle is branched.These characters support the genus Adenocaulon to be the tribe Adenocauleae.The twin-hair exists on the cypsela of the genus Leibnitzia.The mesocap is composed of dispersed sclerenchymatous cell bundle.Banded thickening encircles a ring on the transverse and radial walls of the outermost cell layer of the testaCarduoideae.The subfamily includes Cardueae sensu lato.The phylogenetic tree constructed based on the morphological characters and ITS sequence reveal Cardueae sensu lato is monophyly.The subtribe Echinopsidinae and Carlininae are sister group.The non-glandular trichome and twin-hairs exist on both cypsela.Their mesocarp and testa are composed of parenchyma cell.The secretory cavity lies near the phloem in the midvein of the subtribe Centaureinae and Carduinae..The single crystal exists in the innermost layer of the mesocarp.The outermost layer of the testa is sclereid with radially elongated.The biseriate multicellular glandular trichome occurs on the pappus of the subtribe Centaureinae only.Pertyoideae.The subfamily includes the genus Myripnois.The T-shaped non-glandular trichomes occur on the leaf.The twin-hair and biseriate multicellular glandular hairs exist on the cypsela.The exocarp cell is honeycomb in surface view and the mesocarp is composed of the dispersed sclerenchymatous cell bundles.The outermost cells of the testa are slightly lignified and vascular bundle is branched.Asteroideae.The subfamily includes 11 tribes.The phylogenetic relationship of some taxa are supported by morphology and ITS sequence.Anthemideae is the sister group with the remaining taxa in the subfamily Asteroideae.The T-shaped non-glandular occur on the leaf of the tribe Anthemideae.The secretory cavity is mainly near the xylem in the midvein.The cypsela has no pappus.The exocarp differentiates into mucilage and non-mucilage cells in patial taxa,such as Artemisia,Filifolium,Matricaria and Seriphidium.The Astereae is the sister group with Senecioneae and Gnaphalieae.The Astereae is the sister group witn Senecioneae and Gnaphalieae.The outermost cell of the testa of Asterea is sclereid,which is rectangle with radial or tangential elongation,or inverted U-shaped.The tribe Gnaphalieae and Senecioneae are closely related with each other.The uniseriate multicellular non-glandular trichome with whip-like terminal cell occurs on the leaf of both tribes.The twin-hair with round terminal cell covers on the Gnaphalieae cypsela,the same as Senecio ambraceus var.glaber and S.vulgaris(Senecioneae).The analysis of ITS sequence reveals The tribe Inuleae is the sister group of Athroismeae and Heliantheae alliance(Coreopsideae,Tageteae,Heliantheae,Millerieae and Eupatorieae)respectively.However,The phylogenetic tree constructed based on the morphological structures reveals the tribe Inuleae is the sister group with Astereae,Senecioneae and Gnaphalieae.The exocarp of the Inuleae taxa contains single crystal.The mesocarp is composed of the parenchyma and sclerenchyma cell bundle.The Heliantheae alliance is monophyly.The mesocarp consists of three parts: parenchyma cells in the outer layer,sclerenchyma cells in the middle layers,residual cells in the inner layer,and the phytomelanin lies between the outer and the middle layer.The twin-hair exits on the suface of Athroismeae cypsela,one of the terminal cell has a coiled or hook-like apical tip.The mesocarp is composed of the dispersed sclerenchymatous cell bundles.The systematic position of the Heliantheae alliance and the tribe Athroismeae is uncertain.The morphological structure of the leaf,cypsela and seed of four subfamilies of Asteraceae in Northeast China were observed in this study,In this research,the morphological study of Asteraceae taxa in Northeast China is further completed,reveal the value of these morphological structures used for systematic study,the partial morphological result is supported by molecular systematics,provide the morphological evidence for ITS sequence analysis and contribute to construct the classification of Asteraceae in Northeast China combined morphology with molecular phylogeny.