| Larix chinensis Beissn is the endemic plant that distributed on hightest-altitude top in Qinling Mountain and has been listed one of rare and endangered plants on China Red Data Book. Based on the data and our field investigation, it is showed that the individual number of L. chinensis Beissn is very small and these plants only distribute on a few mountains. Generally, L. chinensis Beissn is the glacial relict of the Quateranry. After the earth has been covered by galciation for long time, the Pinaceae is the first occurred wood tree. So it is necessary for us to study the phylogeny of Larix and the phylogenic position of L. chinensis.rbcL and matK gene are chloroplastic genes. rbcL gene encodes the large subunit of Rubisco. matK lied in the trnK intron and the maturase encoded by this gene participates the RNA II introns splicing. Now these tow genes have been widely used in the phylogenic analysis of plant.Firstly, we amplifed the rbcL and matK gene of L. chinensis Beissn, L.potaninii var. macrocarpa Law, L. principis-rupprechtii Mayr and thenresearched the phylogenic position of L. chinensis Beissn combining thePinaceae sequences shared in the Internet. During the anglicizing process,we applied many softwares such as Chromas, SeqVerter, DNASI 2.5,ClustalX 2.0, Mega 2.0 and POUP 4.0 *. The results were as follows:1. rbcL and matK gene were different from the base constitution. In rbcL,position #1 included more GC than matK as well as position #3 of matKincluded more GC. Three positions of rbcL were under the samemutation effect and the position #1 of matK was undergoing moremutation effect than the other positions. The base substitution of rbcLtook place more easily on position #3 while the substitution of matKtook place on 3 positions equally. The base transversion (TV) of rbcLtook on saturation state and the transversion (TV), transition (TS) ofmatK were lined with p-distance.2. On the phylogenic tree based on rbcL and matK, Abies, Keteleeria and Pseudolarix were always clustered together. On rbcL tree, Cathaya had tight relation with Pinus and on matK tree, Cathaya clustered with Picea.3. On the phylogenic tree based on rbcL + matK, the Larix took part into tow clades: the Sect. Larix clade and Sect. Multiseriales clade. L.kaempfer and L. laricina had tight relations. Because rbcL and matK all lied on chloroplastic genome and they had similar evolution mode we did not gain the phylogenic position clearly. This was also because we had limited time, little expense and deficient data. But we could get ideal result if we combined nuclear gene and mitochondrial gene sequences.4. During the analyzing process, we applied distance method (neighbor joining method) and characteristic data analysis method (maximum parsimony method). And we got similar results such as Abies, Keteleeria and Pseudolarix were always clustered together firstly. The phylogenic tree by maximum parsimony method showed the more acceptable relationship than that of by distance method though it also had not resolved the phylogenic problem.Secondly, we studied the DNA extracting conditions of different plant materials and the PCR-SSCP conditions of rbcL, matK. Single-strand conformation polymorphism (SSCP) is a method for detecting mutations by sensing conformational differences between mutant and normal DNAs in the single-stranded state using non-denaturing polyacrylamide gel electrophoresis. So SSCP also could detect whether or not DNA fragments are identical in sequence. PCR-SSCP is the analysis method for denatured PCR produce in non-denaturing polyacrylamide gel electrophoresis. The results were followed:1. There was different extracting effect for different plant parts and different tissues or organs should use different extracting method: conifer, non-lignified treetop and seedling should adopt CTAB method while seed should adopt Proteinase K method. We attempted to extract D...
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