Botanisches Institut der Universität Heidelberg, Heidelberg, Germany.
Planta. 1972 Sep;107(3):247-56. doi: 10.1007/BF00397940.
The elongation growth in etiolated, intact seedlings and excised hypocotyl segments of Sinapis alba is inhibited by FdUrd in the same fashion, and in either case there is a direct correlation between FdUrd concentration and inhibition of elongation growth. Removal of the roots reduced elongation; however, the percentage inhibition by FdUrd remained the same. Therefore, the growth inhibition by FdUrd is not a consequence of root growth inhibition.The growth inhibition in excised hypocotyls cultured on synthetic media is inversely proportional to the size of the segments, and of the seedlings from which they are taken. Elongation of the smaller segments is more sensitive to FdUrd than that of the larger ones. Anatomical observations showed that the inhibition of growth elongation by FdUrd in the hypocotyl segments is due to inhibition of cell elongation, and not of cell division. Root formation is inhibited in all isolated segments.The growth inhibition by FdUrd could be reversed by dThd but not by uridine, and this reversibility depended upon the FdUrd concentration. When FdUrd inhibition is partial (up to 10(-7)M) relatively high dThd concentration (up to 100 fold) are required for complete reversal; when inhibition is maximal relatively lower dThd concentrations effect a complete or near-complete reversal. Irreversible, unspecific effects of FdUrd were not found.These experiments confirm that DNA synthesis is involved in cell elongation of the hypocotyls even when the apical meristem and roots are removed, and that the growth inhibition by FdUrd is not a nonspecific, toxic effect.
白花菜幼苗的黄化完整植株和切下的下胚轴切段的伸长生长都被 FdUrd 以同样的方式抑制，而且在任何一种情况下，FdUrd 浓度与伸长生长抑制之间都存在直接的相关性。去除根会减少伸长；然而，FdUrd 的抑制百分比保持不变。因此，FdUrd 的生长抑制不是根生长抑制的结果。在合成培养基上培养的切下的下胚轴中的生长抑制与片段的大小成反比，与它们所取自的幼苗也成反比。较小片段的伸长对 FdUrd 比较大片段更敏感。解剖学观察表明，FdUrd 在下胚轴片段中对生长伸长的抑制是由于细胞伸长的抑制，而不是细胞分裂的抑制。所有分离的片段都抑制根的形成。FdUrd 的生长抑制可以被 dThd 逆转，但不能被尿嘧啶逆转，这种逆转取决于 FdUrd 的浓度。当 FdUrd 抑制是部分的（高达 10(-7)M）时，需要相对较高的 dThd 浓度（高达 100 倍）才能完全逆转；当抑制达到最大时，相对较低的 dThd 浓度可以实现完全或近乎完全的逆转。未发现 FdUrd 的不可逆、非特异性作用。这些实验证实，即使去除了顶端分生组织和根，DNA 合成也参与了下胚轴细胞的伸长，并且 FdUrd 的生长抑制不是非特异性的、有毒的作用。
