RELATIONSHIP BETWEEN STIMULUS INTENSITY AND ORIENTED PHOTOTACTIC RESPONSE (TOPOTAXIS) IN CHLAMYDOMONAS
RELATIONSHIP BETWEEN STIMULUS INTENSITY AND ORIENTED PHOTOTACTIC RESPONSE (TOPOTAXIS) IN CHLAMYDOMONAS
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DOI：
10.1111/j.1399-3054.1971.tb01453.x
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发表时间：
1971-01-01
影响因子：
6.4
通讯作者：
CURRY, GM
中科院分区：
文献类型：
--
作者：
FEINLEIB, ME;CURRY, GM
用两种技术研究了衣藻刺激强度与定向趋光反应(拓扑趋光性)之间的定量关系。细胞群体的净反应是用光度法监测的，并随时间连续记录。在显微镜下观察单个细胞的反应，并在胶片上记录它们的游泳轨迹，群体的净反应在低刺激强度时为正，在高强度时为负。通过提高或降低强度，可以在两秒内反转反应方向。趋光性的强度-反应曲线与向光性的剂量-反应曲线相似。净反应没有明显的阈值，它随着对数强度的增加而线性增加，然后下降，最后变为负值。单个细胞的研究表明，净局部定向反应的强度依赖性增加主要是由于响应的细胞数量的增加及其游泳路径的直接性。随着刺激强度的增加，无论净反应在测试的强度范围内是正的，还是在该范围内是负的，或者从正到负，游泳路径与刺激束变得越来越好地对准。游泳率的变化对净反应的强度依赖的变化没有显著的贡献。游泳率在正向地形趋势性强度范围内几乎没有变化，在负向趋势性强度范围内仅有小幅增加。然而，经常在刺激开始时观察到游泳率的一过性下降(停止反应)。讨论了这些结果对取向机制的影响。
Two techniques have been used to study the quantitative relationship between stimulus intensity and oriented phototactic response (topotaxis) inChlamydomonas. The net response of a cell population was monitored photometrically and was recorded continuously against time. The responses of individual cells were observed through a microscope and their swimming tracks were recorded on film.The net response of the population is positive at low stimulus intensity and negative at high intensity. The direction of response can be reversed within two seconds by raising or lowering the intensity. The intensity‐response curve for phototaxis is similar to the dose‐response curve for phototropism. The net response has no distinct threshold; it increases linearly with log intensity; then it decreases and finally becomes negative.The individual‐cell studies reveal that the intensity‐dependent increase in net topotactic response is due primarily to an increase in the number of cells responding and in the directness of their swimming path. As stimulus intensity is raised, the swimming path becomes increasingly well‐aligned with the stimulus beam, whether net response is positive throughout the intensity range tested, negative throughout that range, or changing from positive to negative.Changes in swimming rate do not contribute significantly to the intensity‐dependent changes in net response. Swimming rate shows virtually no change throughout the intensity range of positive topotaxis and shows only a small increase in the negative range. However, a transient decrease in swimming rate (stop response) is often observed at the onset of stimulation. The implications of these results for the orientation mechanism are discussed.