Hader D P, Rosum A, Schafer J, Hemmersbach R
Institut fur Botanik und Pharmazeutische Biologie der Friedrich-Alexander-Universitat, Erlangen, Germany.
J Plant Physiol. 1995 Jul;146(4):474-80.
Gravitactic orientation was investigated in the unicellular photosynthetic flagellate, Euglena gracilis, under different accelerations between 0 and 1.5 x g during a recent space flight on board the American shuttle Columbia. The threshold for gravitaxis was found at < or = 0.16 x g. Above the threshold the precision of orientation increased with acceleration in a sigmoidal fashion and reached saturation at about 0.32 x g, a behavior typical for physiological receptors. At accelerations above the saturation point the cells were closely aligned with the gravity vector (negative gravitaxis) and deviated more and more as the acceleration decreased. Obviously the gravireceptor responds to an error signal that elicits a course correction, again indicating the involvement of an active physiological gravireceptor. No adaptation of the cells to the conditions of weightlessness could be observed over the duration of the space mission (12 days). After landing, the cells showed a normal gravitactic behavior at 1 x g.
在最近一次搭乘美国哥伦比亚号航天飞机的太空飞行中，研究了单细胞光合鞭毛虫纤细裸藻在0至1.5 x g不同加速度下的趋重力定向。发现趋重力的阈值为≤0.16 x g。高于阈值时，定向精度随加速度呈S形增加，并在约0.32 x g时达到饱和，这是生理受体的典型行为。在高于饱和点的加速度下，细胞与重力矢量紧密对齐（负趋重力），且随着加速度降低偏差越来越大。显然，重力感受器对引发航向校正的误差信号作出反应，再次表明存在活跃的生理重力感受器。在太空任务持续期间（12天），未观察到细胞对失重条件的适应。着陆后，细胞在1 x g时表现出正常的趋重力行为。
