Comparison of Leaf Structures in the Green and Yellow Parts of Liriodendron tulipifera ‘Aureo marginatum’ Comparative Investigation of Vessel Elements in the Secondary Xylem of Liriodendron Identification of Liriodendron tulipifera, Liriodendron chinense and Hybrid Liriodendron Using SpeciesSpecific SSR Markers Isolation and Cultivation of Protoplasts of Liriodendron tulipifera The Embryological Studies of Interspecific Hybrids between Liriodendron tulipifera L, and L. chinense(Hesml.)Sarg. Cloning and Bioinformatics of Chalcone Synthase Gene (CHS) in Liriodendron tulipifera and Characterization of Its Tissue Expression