[Effects of the enhanced UV-B radiation on the body cell mitosis of the wheat].

The chromosomal mutation and mitosis of the wheat (Triticum aestivum, cv. 93-4736) were observed under the condition of the enhanced ultraviolet-B radiation. The results showed that the number of cells in mitosis of the UV-B treatments was 68.09% of the control, indicating that the UV-B treatment significantly inhibited division of root tip cells in wheat. Using t-test at P < or = 0.05, there was a significant difference between the control and the treatments. The enhanced UV-B significantly increased aberration frequency of chromosomes and cells (t = 9.51, n = 3, P < 0.05). Several types of chromosomal aberration such as lagging chromosomes of chromosomes bridge, fragments, nuclear aberration occurred in both of control and UV-B treatment. However, the frequency of lagging chromosome and fragments of chromosome was increased significantly by enhanced UV-B radiation (P < 0.05). Furthermore, the UV-B treatment caused several new types of chromosomal aberrations, such as three-bundle, four-bundle and six-bundle. In our opinion, these new types of chromosomal aberrations should be called 'partition-bundle division'. Under the condition of UV-B treatment, the amount of aberrations only accounted for 2.84% of the total during the interphase. In the period, nuclear abnormality appeared mainly in forms of micronucleolus and polycaryon. In the metaphase, there mainly exist fragment chromosome, which accounted for 26.67% of the total aberrations, being secondary to lagging chromosomes. The amount of chromosomal abnormality in the anaphase and telophase was the biggest, which included the types of bridge, lagging chromosomes, etc. Among the types, the lagging chromosomes were dominant, accounting for 32.84% of the total. In this study, what was especially emphasized was the UV-B induced abnormal mitosis that was first found. In the anaphase and telophase of the treated cells, chromosomes were divided into 3 bundles, 4 bundles, or 6 bundles, respectively accounting for 8.77%, 15.43%, and 8.02% of the total abnormal cells. Three-bundle division was nonsymmetrical. The number of chromosomes in each of the three bundles was not completely equal. Four-bundle division mainly symmetrized at direction of axis, the number of each of the two bundles on the same axis was basically the same, but was different from that on another axis. Four-bundle division was conducted in two patterns of division. With respect to the much more special six-bundle division, chromosomes were regularly divided into 3 groups, symmetrizing each other. As viewed from the number of chromosomes in each bundle, it was smaller than that in normal somatic cells. In the abnormal division of cells, cell plate or cell wall between the two divided bundles was not found, leading to 'multi-bundle bodies' occurrence by the end of cell division. Therefore, the abnormal division of the somatic cells should be called 'the multi-bundle division' or 'the partition bundle division'.