Karyotype Analysis of Root Chromosome in Three Species of Styrax

Seeds of Styrax odoratissimus, S. tonkinensis and S. confusus were collected on September and October of 2013 in Hangzhou, Zhejiang province. They were treated by sand storage until the next spring. When seeds germinated and root had 3-5 cm, the apices of three species were used for chromosome sectioning and karyotype analysis. The results showed that the tested species were diploid, and their genome chromosome number was 2n=2x=16. Karyogram of S. odoratissimus was 2n=16=10 m+6 sm (sat), nuclear asymmetry index was 58.20%, and karyotype was 2A. Karyogram of S. tonkinensis was 2n=16=12m(1sat)+4sm(2sat), nuclear asymmetry index was 53.09%, andt karyotype was 1A. Karyogram of S. confusus was 2n=16=12 m(1sat)1+4 sm, nuclear asymmetry index was 56.54%, and the karyotype was 1A. The test concluded that karyotypes of S. tonkinensis and S. confusus were similar, but different with that of S. odoratissimus, indicating that the chromosome evolution of three species was low, and they were primitive.