| Dandelion (Taraxacum F.H.Wigg), which one of the Compositae's big family, belongs the Subfam. Liguliflorae DC as well, is the most evolutive taxon around the world. This paper refers a taxonomy study of ten Dandelion species in northeast of China where its resource is numerous. Based on the traditional systematics, by using anatomy, micromorphology, palynology, cytology, chemistry and molecular systematics as assistant tools to analysis and contrast, we discussed taxonomic relationship and genetic relationship of this family at the same time, and supply more scientific and reasonable evidence of it. The main results of it as follow.1. Perfect and the supple the taxonomy keys of dandelionBy using the method of morphologic observation, this study confirms the characteristic of flower, leaf, achene, and etc in morphology; describes the whole terms and keys of taxonomy on each organ of the plant carefully; sums up and conclude the detail information of the ten dandelion species on botany describing. Meanwhile, this paper point out that the'ratio of mouth and bottom in length','ratio of bract and horn in lengh'and?uality of leaf' should be looked as the keys or basement of taxonomy as well to perfect or supply the evidences of dandelion on taxonomy.'rate between mouth and bottom'means the rate between mouth length and achene length of dandelion, which using the B (mouth length):A (achene length) to indicate it, and this rate always range from1:5to1:2. Among of this ten species, T. antungense Kitag. and T. urbanum Kitag. own the smallest rate—1:5; T. variegatum Kitag.s rate is the biggest—1:2. The feature by many repeat experiments have stability and reliability.'rate between bract and horn'means the rate between the degree of horn belongs to the outer bract at the fullbloom stage and the size of the achene after riping, i.e. the tuber on the outer bract at the fullbloom stage is bigger, the achene which the plant has will be larger, and this characteristic has been proved in the test. The quality of leaf means that the shape of the apex of shred leaf; whether the small leaf has in the each two shred leaf; whether the crack on the leaf is big or small, and we could use this key to identify the dandelion.2. The classification evidence of genomicThe study of chromosome set learning in dandelion indicates that, the amount of chromosomes in dandelion is16,24,32. T. ohwianum Kitag. is diploid, number of its chromosomes is16, karyotype formula is2n=2x=2m(SAT)+6m+8sm; the tetraploid dandelions includes T. mongolicum Hand.-Mazz, T. formosanum Kitam, T.coreanum Nakai., T. liaotungense Kitag., T. variegatum Kitag., and the number is32, karyotype formula of T. variegatum Kitag. is2n=4x=12m+20sm; T.coreanum Nakai.'s is2n=4x=24m+8sm; the rest of three other species's is2n=4x=24m+8sm, in addition, T. antungense Kitag, T. urbanum Kitag. share one karyotype formula which is2n=3x=12m+3sm(3SAT)+12sm, T. asiaticum Dahlst., T. asiaticum var.lonchophyllum Kitag.'s is2n=3x=3m(3SAT)+18m+3sm, both are triploid which number is24. and karyotype of T. ohwianum Kitag. and T. variegatum Kitag. are'2B', the rest of other eight species's karyotype is '1A'.3. The evidence of molecular systematics classification in dandelionThis study adopt the method of ITS sequence analysis, for sequence testing on ten species of dandelion in northeast China, and built a ITS phylogenetic tree of dandelion. The result indicated that:the mean length of dandelion species is730bp, among of them, ITS1region length is about276bp, ITS2region length is about294bp, the content of5.8S rDNA is162bp. The content of G+C's difference among all kinds of these species is not very big, among of them, the T. ohwianum Kitag.'s is the smallest, which is51.23%, and by the contrast, the T.coreanum Nakai.'s is the biggest, which is52.53%. The phylogenetic tree depart as two big monoids, which their bootstraps are79%and100%, respectively. The biggest index of difference is0.051, means that the difference between T. ohwianum Kitag. and T. formosanum Kitam. is large; the smallest index of difference is0.007, means that T. liaotungense Kitag. and T. variegatum Kitag. has the small gap.4. The classified merging and evolve trend among dandelion familyThe study on taxonomic identification of Taraxacum species in northeast of China includes ten Dandelion species, such as T. antungense Kitag., T. urbanum Kitag., T. ohwianum Kitag., T. variegatum Kitag., T. asiaticum Dahlst., T. asiaticum var.lonchophyllum Kitag., T. mongolicum Hand.-Mazz., T. formosanum Kitam., T. liaotungense Kitag., T.coreanum Nakai.. The results show that T. urbanum Kitag. should be merged into T. antungense Kitag., T. asiaticum var.lonchophyllum Kitag. should be merged into T. asiaticum Dahlst., T. liaotungense Kitag. and T. formosanum Kitam. should be merged into T. mongolicum Hand.-Mazz..The morphology characteristics of pollen can reflect the evolutionary trend of Taraxacum species, perfectly. The study shows that the evolution law of ornamentation is relatively primitive pollen exine always generally smooth. Then it appears ornamentation (such as microperforation and microfoveolation, ect.), furthermore, it produces processes (such as rough or granular, ect.) in the exine, thus evolved into rodlike, drumsticklike, clostridium or spinelike, and etc., and form nets, ripples, striation. As all of this, dandelion belongs to the evolve taxon. The micromorphological features of achene can also reflect the evolve trend and type of the plant. From the view of evolve trend of dandelion, the main characteristic of evolve in dandelion is:tip of achene has mouth, the mouth is short and not obvious, the evolve one is long, thin and obvious; no tumours or little stabs on the wall of achene, and the evolve one has tumours or little stabs on the wall of achene. Therefore, the characteristic of dandelion achene reflects that, the dandelion belongs the evolve one. |
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