| Platycladus orientalis(L.) Franco was an important tree species for afforestation and greening in China with the resistance of drought and barren, which was also an important species in limestone mountain area. The research of different geographical provenances of Arborvitae was in order to explore the growth performance of provenances and adaptation to environments, and select excellent provenances. So as to provide a scientific evidences for seed transfer reasonable.In this paper, the forty-four different geographical provenances of Arborvitae which were taken as the experimental materials are from Dazhai Shan Forest center which located in Pingyin County and Yuan Shan Forest center of Zibo City. Based on the experiments, the conventional squashed method was improved and the somatic-cell-chromosomes of Arborvitae were studied. Through the identification of chromosome number, analysis of karyotypes and exploration of effective approach on karyotype analysis to all geographical provenances, we provided the basic cytology data of different geographical provenances of Arborvitae. The main results were as follows:1. According to the existing plant cytological research results, we have improved the study methods of chromosome and explored a simple, economical and efficient karyotype analysis method. The new shoots were collected in clear days in March or April of the spring from 9:00 AM to 16:00 PM and the shoots should be 1~2 mm. Tender tissues were pretreated with saturated 1,4 dichlorobenzene solution for 8~9h, and during the process the solution should be changed for 2~3 times; or for 20~24h in fixed freshly prepared Carnoy's and fixed liquid(1:2 acetic-alcohol); or disrobe the outside scale leaves under Microscope and hydrolyzed in 1mol/L HCL solution for 10 min in 60℃water bath. Stained with improved fuchsin solution. Squashing, microscopic examination and then measurement. The pairing and arrangements of chromosomes were made using Adobe photoshop and Auto CAD.2. The results showed that all the chromosomes of different geographical provenances of Arborvitae were diploid and the number was 22, and the actural lengths of chromosomes were medium-long chromosomes. The main karyotype was m chromosome and only Yili of Xinjiang had sm chromosomes. The ratio was 18.1, which was the longest chromosome to the shortest chromosome between 2 and 4. There were no chromosomes which the arm ratio more than 2. As to relative length, the karyotype have S chromosome,M chromosome and L chromosome, and the majority are M chromosomes. The varation of asymmetric coefficient ranged 50.81%~54.48%. All of the karyotype of the geographical provenances of Arborvitae belonged to 1A type, and the species were stable and symmetry. There was great similarity of karyotype among the provenances.3. The results from the evolution trend map of karyotype showed that, Wenshui of Shanxi, Chunhua of Shanxi and Yili of Xinjiang were more evolved than Zunhua of Hebei, Huolu of Hebei and Pingyin of Shandong. The results of cluster analysis indicated that the minimum genetic distance (0.1) was between Dengfeng of Henan and Lingbao of Henan, and the maximum genetic distance (0.78) was between Huolu of Hebei and others. Based on the similarity on chromosome features, the 44 provenances can be divided into three classes. In Shandong province, Taian was more evolved than Pingyin and Lingyan. The results of cluster analysis indicated that the minimum genetic distance (0.28) was between Taian and Yiyuan, and the maximum genetic distance (0.78) was between Zhangqiu and others. The 11 provenances in Shandong also can be divided into three classes. Correlation analysis showed that, there were highly significant negative correlation between the average arm ratio and longitude, and significant negative correlation between the asymmetrical karyotype and longitude, while there were significant correlation between average arm ratio and latitude. In China, the provenances in west and north area were evolutionary. However, the relationship of geographic variation of Arborvitae provenances was not linearity, which need more accurate model to express the complex variation trend.
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