花生种子萌发早期胚轴细胞DNA合成的特点

花生种子吸胀6h后胚轴DNA中有~3H-胸苷掺入。咖啡因和羟基脲均对6～12h的~3H—胸苷掺入具强烈的抑制作用;当12～24h时,咖啡因的抑制作用较大;但30h以后,羟基脲的抑制作用超过咖啡因。双链DNA放射性从种子吸胀9h后迅速上升,单链DNA放射性在吸胀12h后出现一个明显的峰。但在吸胀12h后,单链DNA形成和存在的时间是短暂的。

Analysis of the Character of the DNA Synthesis in Axis of Peanut Seeds During Early Germination

The aim of this paper was to con-firm that the incorporation of ~3H-thymidine into embryos of seeds duringearly germination included DNA re-pair. The experimental materials wereseeds of cultivar "Yue-you 116" ofpeanut (Arachis hypogaea L.). Caffeineand hydroxyurea were used to inhibitDNA synthesis, and batch method us-ing hydroxylapatite was used for theseparation of DNA. DNA synthesiswas studied by following the rate of~3H-thymidine incorporation into TCA-precipitated substances. A peak of DNA synthesis oc-curred after imbibition for 12 h beforethe semiconservative genomic DNAreplication accompanied by an increaseof the DNA content in axis and thegrowth of radicle. Different to thesemiconservative replication, the DNAsynthesis within 12 h was inhibited bycaffeine and by hydroxyurea to almostthe same extent, and the DNA synthe-sis between the 18th and the 24th hourof imbibition was inhibited by hydrox-yurea and more effectively by caf-feine, whereas the inhibitory effect ofhydroxyurea was more effective thanthat of caffeine after imbibition for 30h (Fig. 1). By separation with hy-droxylapatite, DNA synthesis betweenthe 9th and the 27th hour appearedmainly in the double-stranded DNA re-gion and only some in the single-stranded DNA region, and a peak wasobserved in the single-stranded DNAregion at the 12th hour (Fig. 2). Ifthe duration of labelling was less than40 min, the radioactive activity of sin-gle-stranded DNA was higher than thatof double-stranded DNA, whereas, asthe labelling time was prolonged, theradioactive activity of double-strandedDNA increased rapidly and that of sin-gle-stranded DNA remained practicallyunchanged (Fig. 3). The DNA synthesis in axis ofpeanut seeds during early germinationseems to be quite complicated. The in-corporation of ~3H-thymidine into DNAof axis during early germination mayreflect DNA replication and DNA re-pair events occurring at the same time.