Studies on Taxonomy of the Genus Seriphidium in China
|School||Northwest University of Science and Technology|
|Keywords||Seriphidium Fruit micro-characteristics Pollen morphology Karyotype Flora|
The genus Seriphidium, belonging to the tribe Anthemidae of Composite, there are more than 130 species distributed in Asia-Europe continent, North America and North Africa of temperate to boreal regions of the North Hemisphere. About 31 species, 3 varieties according to the record of Flora Reipublicae Popularis Sinicae in vol 76, No.1 which were classified into 3 Sect, namely, Sect. Juncea, Sect. Seriphidium, Sect. Minchünensa. They distributed mainly northwest arid of China, west areas of North America, the Middle East and North Africa. Seriphidium have important value in medicinal, fodder and ecology, moreover, some possess important affect on population regulation in northwest arid prairie, having immense potentialities in developing.From Seriphidium divided from Artemisia by Polkakov in 1961, only Lin yourun contributed to it in taxonomy. Even so, there still various problems needed to further research. We have put emphasis mainly on anatomy, micro-characteristic of fruit, sporopollen, etc. to study, and the major achievement obtained as follow:1. Comparative on main characteristics of systematic botany between Seriphidium and its 10 genus allies.The results show that Seriphidium and Artemisia have the near genetic relationship comparatively, but their monoclinic are entirely different, which illustrate clearly that Seriphidium and Artemisia is two different plant categories; possess the different characteristics obviously between Seriphidium and its 9 genus allies. As a separate unit of genus for Seriphidium are reasonable. Base on the results above, we also discussed the evolution of Seriphidium, and we put forward a proposal to establish the Ser. finitum.2. The micro-characteristics of fruit were studied under LM and SEM. The results that the micro-characteristics of fruit from Seriphidium and its allies show rich variety, especially on the ornamentation of fruits between genuses; the consequence have produce new proof for controversy genus, such as Elachanthemum, Neopallasia, Chrysanthemum, to as a independently unit of genus; there have distinct distinguish between Seriphidium and its allies in micro-characteristics of fruit, consequently we hold Seriphidium as a genus is reasonable. Resembled in micro-characteristics of fruit between Seriphidium and Artemisia reflect their genetic relationship.3. Pollen morphology of taxa of the genus Seriphidium, distributed in China, was studied with LM and SEM. The results show that the shape of pollen grains are prolate, spheroidal or subspheroidal in equatorial view, and three-lobed in polar view; the size of pollen grains was 22.52(16.23 ~ 27.18)μm in the polar axis and 17.22(15.51 ~ 23.13)μm in the longest equatorial, the average of P/E is 1.31; the apertures are three-colporate, which extended to polar area and no converged (except the un-identified species); exine is composed with two layers under LM and the outer lawyer often thicker than the inner; the ornamentation of the exine is coarse under LM and is spinule-granular. The systematic significance of pollen morphology is discussed in the end.4. The karyotype analysis of 13 species from Seriphidium, distributed in China, were studied, and the results show all 13 species have diploid characteristic of karyotype and the cardinal number is 9, exception S. schrenkianum and S. transiliense (2n=36), other 11 specie were 2n=18. The type of karyotype can be divided 2A and2B (only S. schrenkianum and S. transiliense). The number and position of SAT are different between species to some extent. According to the principle of symmetrical characteristic by Stebbins, the orientation of evolution of 13 species, from symmetry to dissymmetric, is : S. junceum, S. transiliense, S. issykkulense, S. schrenkianum, S. kaschgaricum, S. sawanense, S. cinum, Seriphidiun minchünense, S. sublessingianum, S. santolinum, S. gracilescens, S. amoenum, S. terrae-albe. Stand by regarding S. junceum as the most original species in Seriphidium; proposal reverses the position of S. transiliense and S. schrenkianum. The karyotype analysis of 13 species is report first time.5. By check a large number of specimen, field work and indoor experiment, we have record much information. Base on it, we fix 31 species, 5 varieties distributed in China.6. Discussed the distribution present in China, Flora, the pattern of distribution, etc. Conclusion: the distribution of Seriphidium in China has obvious feature of region, Xinjiang province is the center of contemporary distribution; the available fossil record and sporopollen prove that Seriphidium and Artemisia have the identical origin place which may be located desert steppe or arid forestry of Wulaer Mt. in sub arctic; from divided from its ancestor, Seriphidium plants have three migration from the origin center, namely, east, west and south, the motive power of migration is the gradual changes of geology and stress of glacial epoch; the pattern of distribution in China present“three-band”, that is Aletai-Kelamayi nearby Aertai Mt.; Yining-wulumuqi-Hami nearby Tian Mt.; Keshi-Akesu-Hetian nearby Kunlun Mt.. The substitution between species in different region is obvious; the route of migration is from north to south in vertical, and from west to east in lateral. The flora of Seriphidium in China can be divided two districts, including five sub districts.