In this test,common wheat root tips were treated with hypoxia water to explore the effects of hypoxia on nucleolar structure and function of root-tip meristematic cells of common wheat using serials of techniques,such as conventional cell preparation,silver staining,electron microscopic observation,indirect immunofluorescence staining and RT-PCR analysis.It was observed that,after hypoxia water treatment,(1)the nucleoli in the meristematic cells became swell,protruded and agglutinated;some inner vesicular and abnormal nucleolar channels appeared;the fine structures of the nucleolus were disappeared and even more,the nucleolus was segregated,etc.(2)Nucleophosmin B23 shuttled from nucleoli to nucleoplasm,even to cytoplasm revealed by indirect immunofluorescence staining techniques.(3)RT-PCR analysis indicted that the expression level of rRNA gene was lower obviously than that of control and the expression signal of C23 was undetectable.It means that the expressions of both ribosomal RNA and C23 genes were down-regulated significantly.Our results demonstrate that hypoxia treatment can not only damage nucleolar structure but inhibit its function.