Sailer H, Nick P, Schafer E
Institut fur Biologie II, Freiburg, Federal Republic of Germany.
Planta. 1990 Feb;180(3):378-82. doi: 10.1007/BF00198789.
Gravitropic stimulation of maize (Zea mays L.) seedlings resulted in a continuous curvature of the coleoptiles in a direction opposing the vector of gravity when the seedlings were rotated on a horizontal clinostat. The orientation of this response, however, was reversed when the gravitropic stimulation was preceded by symmetric preirradiation with blue light (12.7 micromoles photons m-2). The fluence-response curve of this blue light exhibited a lower threshold at 0.5 micromole m-2, and could be separated into two parts: fluences exceeding 5 micromoles m-2 reversed the direction of the gravitropic response, whereas for a range between the threshold and 4 micromoles m-2 a split population was obtained. In all cases a very strong curvature resulted either in the direction of gravity or in the opposite orientation. A minor fraction of seedlings, however, curved towards the caryopsis. Furthermore, the capacity of blue light to reverse the direction of the gravitropic response disappeared with the duration of gravitropic stimulation and it depended on the delay time between both stimulations. This tonic blue-light influence appears to be transient, which is in contrast to the stability observed for tropistic blue-light effects.
当玉米（Zea mays L.）幼苗在水平回转器上旋转时，向重力刺激会导致胚芽鞘持续弯曲，弯曲方向与重力矢量方向相反。然而，当在向重力刺激之前用蓝光（12.7微摩尔光子·平方米⁻²）进行对称预辐照时，这种反应的方向会反转。这种蓝光的光通量-反应曲线在0.5微摩尔·平方米⁻²处表现出较低的阈值，并且可以分为两部分：光通量超过5微摩尔·平方米⁻²会使向重力反应的方向反转，而在阈值和4微摩尔·平方米⁻²之间的范围内会得到一个分离的群体。在所有情况下，都会产生非常强烈的弯曲，要么是朝着重力方向，要么是相反方向。然而，一小部分幼苗会朝着颖果弯曲。此外，蓝光使向重力反应方向反转的能力会随着向重力刺激的持续时间而消失，并且它取决于两种刺激之间的延迟时间。这种持续性蓝光影响似乎是短暂的，这与向性蓝光效应所观察到的稳定性形成对比。
