<正>CT图像中灰度大小与木材密度成正比。径切面上的木材密度变化不大，但缺陷出现时会有大幅变化。笔者依据以上的木材特性，以欧洲白腊为例利用三次自然样条函数对原木CT扫描三维数据重构，比较了有间隔和没有间隔的函数插值的数据。结果表明：进行原木CT图像采样时，适当的间隔可以提高CT的扫描效率和图像的处理速度，且能降低成本。

In order to distinguish the main Ginkgo cultivars and genetic diversity among them, 44 main Ginkgo eultivars planted in Pizhou Ginkgo Germplasm Garden, Jiangsu, China were sampled and analyzed by molecular marker RAPD and ISSR. These cultivars are planted widely in China. The ISSR results showed that 44 main Ginkgo eultivars could be identified by 16 polymorphie sites amplified by 5 ISSR primers. A computerized ISSR fingerprinting of the 44 Ginkgo cultivars was drawn to facilitate the management of eultivars. The genetic diversity of the cultivar population was studied by RAPD and ISSR. The results showed that the average effective number of alleles, gene diversity and Shannon’s information index revealed were 1. 730 7,0. 410 1 and 0. 596 3 respectively by ISSR, and were 1. 573 5,0. 333 1 and 0. 497 9 respectively by RAPD, which indicated high genetic diversity among the population. ISSR marker was more accurate in assessing the genetic diversity of Ginkgo than that of RAPD. So it indicated that ISSR is a good molecular marker to distinguish Gingko cultivars, and it can be put into practical use when more cultivars are added and more appropriate primers are sequenced. As there exist high genetic diversity in Ginkgo cultivars, it is important to collect as many representative trees planted in different places as possible, in order to protect and exploit them better.