Comparative Anatomy Of Secondary Structure In Nyssaceae

Plant anatomy, FTIR and GC-MS were applied to compare the differences in secondary xylem and phloem structure, cell morphology and chemical components of three species,Camptotheca acuminata, Nyssa sinensis and Davidia involucrata in family Nyssaceae(Engler system) in this paper. Nyssaceae was included in Cornaceae in APGIII system, thus another three species in Cornaceae, Cornus macrophylla, Cornus officinalis and Cornus controversa,were selected to study their genetic relationships with 3 species in Nyssaceae(Engler system)and analyze whether it is proper for taxonomy of Nyssaceae in APGIII system. The results were listed as follows:1. Secondary xylem structures of six species in Nyssaceae and Cornaceae are similar except width of types of rays. They are diffuse-porous with vessels partly solitary, partly radial multiples and clusters. Scalariform perforation plates are commonly more than 20 bars.Opposite intervessel pits are the main type of pits between vessel elements without helical thickness. Axial parenchyma diffuse. Ray width in tangential section are 2.04(2-3) cells in C.acuminata, 2.14(2-3) cells in N. sinensis, 2.21(2-3) cells in D. involucrate, 2.46(2-3) cells in Cornu. macrophylla, 3.77(2-4) cells in Cornus officinalis and 2.43(2-3) cells in Cornus controversa.2. Vessel length, number of perforation plates and fiber length are different in 6 species while there is no significant difference in cell width. According to IAWA list of microscopic features for hardwood identification, vessel lengths of 6 species belong to the range of ?800?m with order of D. involucrate > N. sinensis > Cornus controversa > C. acuminate > Cornus macrophylla > Cornus officinalis. Number of perforation plates(NPPs) of C. acuminate is less than 20 bars, NPPs of 3 species in Cornaceae are between 20-40 bars while NPPs of N. sinensis and D. involucrate is more than 40 bars. NPPs of D. involucrate is much more than other species though NPPs of N. sinensis and D. involucrate belongs to same level classified by IAWA. Fiber length of 3 species in Nyssaceae belongs to ?1600?m and in Cornaceae belongs to range of 900-1600?m with order of D. involucrate> C. acuminate > N. sinensis > Cornus controversa > Cornus macrophylla > Cornus officinalis.3. Secondary phloem structures of six species in Nyssaceae and Cornaceae are consist of axial(sieve tubes, phloem parenchyma cells, phloem fibers occurs in all other 5 species except D.involucrate) and radial(phloem rays) systems. The occurrence of phloem fibers and their arrangement determine the significant difference in secondary phloem structures. Phloem fibers form in tangential bands in C. acuminate, N. sinensis and Cornus macrophylla and in random island-shape in Cornus officinalis and Cornus controversa.4. Sieve tube, phloem parenchyma and phloem fiber length are different in 6 species while there is no significant difference in cell width. The orders are D. involucrate> N. sinensis> C.acuminate > Cornus controversa > Cornus officinalis > Cornus macrophylla in sieve tube and phloem parenchyma length, C. acuminate > N. sinensis > Cornus controversa > Cornus officinalis > Cornus macrophylla in phloem fiber length.5. FTIR spectra of secondary xylem and secondary phloem samples of six species in Nyssaceae and Cornaceae show that the chemical content of wood flour is basically similar,where as the existence and intensity of some characteristic peaks that reflect lignin have some differences.6. The GC-MS results of the Ingredients and content of significant polar phase metabolites identified from the secondary phloem samples of Nyssaceae and Cornaceae show some differences.Hydrocarbons and oleic acid only exist in the secondary phloem samples of Nyssaceae while aldohexose could only be found in the secondary phloem samples of Cornaceae.Secondary xylem structures show obvious differences among D. involucrate and other species while N. sinensis and C. acuminate show similarity to 3 species in Cornaceae. D.involucrate is proved to be the most original species from the aspect of NPPs and vessel length.Phloem fibers arrange in band or island-shape in secondary phloem of five species, however there is no phloem fiber in D. involucrate. Sieve tube phloem parenchyma length indicate D.involucrate is the most original species which is same as the results in secondary xylem.We conclude that N. sinensis and C. acuminate can be included in Cornaceae while D.involucrate cannot from the aspects of analysis of secondary xylem, phloem and FTIR.However, GC-MS analysis shows there are typical chemical components in two different family respectively indicating the differences in Nyssaceae and Cornaceae. Thus, more researches should be conducted to discuss the taxonomy of Nyssaceae.