In this study,we collected fresh flowers from Cucumis sativus around 10:00^am from June to August,isolated the generative cells (GC) of C.sativus with the method of osmotic shock,quantified its mitochondrial DNA (mtDNA) contents through employing the competitive quantitative PCR technology,and analyzed the change of mtDNA contents in GC during its development,in order to investigate the origin of the abundant mtDNA,and lay the foundation for further study on the molecular mechanism of regulation of mitochondrial DNA amplification in angiosperm.The results showed that:(1)DAPI staining represents abundant fluorescence points of organellar DNA around the nucleus of GC of C.sativus,indicating the presence of a large number of mtDNA in cytoplasm of cucumber GC.(2)The single mature GC of C.sativus averagely owns (1 037±126) mtDNA copies.(3)Compared with early GC,the mature GC upregulates the mtDNA by 14.5 times,suggesting that mtDNA in mature GC is mainly from its active amplification after GC formation.The study suggests that the active increase of mtDNA in GC is the basis of the paternal mitochondrial inheritance of C.sativus.