Van't Hof J, Sparrow A H
J Cell Biol. 1965 Jul;26(1):187-99. doi: 10.1083/jcb.26.1.187.
Actively growing and dormant roots of Tradescantia paludosa were exposed to x-rays to compare the radiosensitivity of an actively proliferating tissue with that of one which is not active but is potentially proliferative. The level of effect was ascertained by the degree of change in the rate of root growth 4 days after exposure. Cell population kinetics were measured in control and in irradiated roots to determine whether or not a change was produced either in the number of proliferating cells or in the mitotic cycle duration which was sufficient to explain the altered rate of root growth. Nuclear volumes were also measured to provide an estimate of the relative total target size in actively growing vs. dormant roots. Tritiated thymidine was used to measure the cycle duration and the proportion of cells synthesizing DNA. The results showed that 184 and 305 r respectively were required to reduce the linear root growth rate to 37 per cent of that of the control for actively growing and dormant roots. Mitotic cycle duration, measured 4 days after x-ray exposure, was the same as in the control. The number of proliferating cells, however, was reduced. The rate of cell production in the irradiated roots was reduced to approximately one-half that of the controls. The average nuclear volumes of active and dormant roots were 733 and 491 micro(3) respectively; thus the difference in the number of roentgens required to reduce growth to 37 per cent of that of the control can be attributed to the different average nuclear volumes. Therefore, the experiments suggest that part if not most of the differences in sensitivity between an actively dividing and an essentially non-dividing meristematic cell population resides in their different average nuclear volumes. Thus the law of Bergonie and Tribondeau needs to be reinterpreted, since the basic reason for the differences is secondary to whether or not the meristematic cells are proliferating.
将生长旺盛和处于休眠状态的紫露草（Tradescantia paludosa）根暴露于X射线下，以比较活跃增殖组织与非活跃但具有潜在增殖能力的组织的放射敏感性。通过照射后4天根生长速率的变化程度来确定效应水平。测量对照根和受照射根的细胞群体动力学，以确定增殖细胞数量或有丝分裂周期持续时间是否发生了足以解释根生长速率改变的变化。还测量了细胞核体积，以估计生长旺盛的根与休眠根中相对总靶标的大小。用氚标记的胸腺嘧啶核苷来测量周期持续时间和合成DNA的细胞比例。结果表明，对于生长旺盛和休眠的根，分别需要184伦琴和305伦琴才能将根的线性生长速率降低至对照的37%。X射线照射后4天测量的有丝分裂周期持续时间与对照相同。然而，增殖细胞的数量减少了。受照射根中的细胞产生速率降低至对照的大约二分之一。生长旺盛的根和休眠根的平均细胞核体积分别为733和491立方微米；因此，将生长降低至对照的37%所需的伦琴数差异可归因于平均细胞核体积的不同。因此，这些实验表明，活跃分裂和基本不分裂的分生细胞群体之间敏感性差异的部分（如果不是大部分）在于它们不同的平均细胞核体积。因此，伯戈尼和特里波多定律需要重新解释，因为差异的根本原因次要于分生细胞是否在增殖。
