Light and dark adaptation in Phycomyces light-growth response.
Light and dark adaptation in Phycomyces light-growth response.
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须霉菌光生长反应中的光适应和暗适应。
DOI：
10.1085/jgp.81.6.845
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Block,SM
中科院分区：
文献类型：
--
作者：
Lipson,ED;Block,SM
真菌Phycommonium的孢子囊细胞表现出对光刺激的适应，动态范围为10（10）。这个范围适用于向光性和密切相关的光生长反应;在后一种反应中，伸长速率通过光强度的变化瞬时调制。我们已经进行了光和黑暗的适应实验，使用自动跟踪机，允许在受控条件下连续测量生长速度的孢子囊。我们根据Delbrück和Reichardt（1956，Cellular Mechanisms in Differentiation and Growth，3-44）的适应模型对结果进行了检验。“适应水平”A是通过一系列强度-反应曲线从对测试光脉冲的反应中推断出来的。在正常光强范围内（10（-6）-10（-2）W/m2），暗适应的衰减时间常数为B = 6.1 +/-0.3 min。然而，在高强度范围（10（-2）-1 W/m2）的暗适应中显示出更高阶的动力学。在这个范围内的适应与预测的模型相关的变化A受体色素的失活和恢复。在正常范围内的强度的步骤，A被发现迅速增加，超调所施加的强度水平，然后放松到该水平在40分钟内。这些结果是不兼容的Delbrück-Reichardt模型或任何简单的概括it. The不对称性和超调是类似的适应现象中观察到的系统不同的细菌趋化性和人类视觉。这似乎是可能的，光和黑暗的适应在Phycomelia介导的完全不同的过程。
Sporangiophores of the fungus Phycomyces exhibit adaptation to light stimuli over a dynamic range of 10(10). This range applies to both phototropism and the closely related light-growth response; in the latter response, the elongation rate is modulated transiently by changes in the light intensity. We have performed light- and dark-adaptation experiments on growing sporangiophores using an automated tracking machine that allows a continuous measurement of growth velocity under controlled conditions. The results are examined in terms of the adaptation model of Delbrück and Reichardt (1956, Cellular Mechanisms in Differentiation and Growth, 3-44). The "level of adaptation," A, was inferred from responses to test pulses of light by means of a series of intensity-response curves. For dark adaptation to steps down in the normal intensity range (10(-6)-10(-2) W/m2), A decays exponentially with a time constant b = 6.1 +/- 0.3 min. This result is in agreement with the model. Higher-order kinetics are indicated, however, for dark adaptation in the high-intensity range (10(-2)-1 W/m2). Adaptation in this range is compared with predictions of a model relating changes in A to the inactivation and recovery of a receptor pigment. In response to steps up in intensity in the normal range, A was found to increase rapidly, overshoot the applied intensity level, and then relax to that level within 40 min. These results are incompatible with the Delbrück-Reichardt model or any simple generalizations of it. The asymmetry and overshoot are similar to adaptation phenomena observed in systems as diverse as bacterial chemotaxis and human vision. It appears likely that light and dark adaptation in Phycomyces are mediated by altogether different processes.