Lee J S, Evans M L
Department of Botany, Ohio State University, Columbus 43210, USA.
Plant Physiol. 1985;77(4):824-7. doi: 10.1104/pp.77.4.824.
The effect of Ca on the polar movement of [3H]indoleacetic acid ([3H]IAA) in gravistimulated roots was examined using 3-day-old seedlings of maize (Zea mays L.). Transport of label was measured by placing an agar donor block containing [3H]IAA on one side of the elongation zone and measuring movement of label across the root into an agar receiver block on the opposite side. In vertically oriented roots, movement of label across the elongation zone into the receiver was slight and was not enhanced by incorporating 10 millimolar CaCl2 into the receiver block. In horizontally oriented roots, movement of label across the root was readily detectable and movement to a receiver on the bottom was about 3-fold greater than movement in the opposite direction. This polarity was abolished in roots from which the caps were removed prior to gravistimulation. When CaCl2 was incorporated into the receivers, movement of label across horizontally oriented intact roots was increased about 3-fold in both the downward and upward direction. The ability of Ca to enhance the movement of label from [3H]IAA increased with increasing Ca concentration in the receiver up to 5 to 10 millimolar CaCl2. With the inclusion of CaCl2 in the receiver blocks, gravity-induced polar movement of label into receiver blocks from applied [3H]IAA was detectable within 30 minutes, and asymmetric distribution of label within the tissue was detectable within 20 minutes. The results indicate that gravistimulation induces a physiological asymmetry in the auxin transport system of maize roots and that Ca increases the total transport of auxin across the root.
利用3日龄玉米（Zea mays L.）幼苗，研究了钙对重力刺激根中[3H]吲哚乙酸（[3H]IAA）极性运输的影响。通过将含有[3H]IAA的琼脂供体块放置在伸长区的一侧，并测量标记物穿过根移动到另一侧琼脂受体块中的情况，来测定标记物的运输。在垂直定向的根中，标记物穿过伸长区进入受体的移动很少，并且在受体块中加入10毫摩尔氯化钙也不会增强这种移动。在水平定向的根中，标记物穿过根的移动很容易检测到，并且向底部受体的移动比相反方向的移动大约大3倍。这种极性在重力刺激前去除根冠的根中消失。当将氯化钙加入受体中时，标记物穿过水平定向完整根的移动在向下和向上方向上均增加了约3倍。随着受体中钙浓度增加至5至10毫摩尔氯化钙，钙增强[3H]IAA标记物移动的能力也增强。在受体块中加入氯化钙后，30分钟内即可检测到重力诱导的标记物从施加的[3H]IAA向受体块的极性移动，20分钟内即可检测到组织内标记物的不对称分布。结果表明，重力刺激在玉米根的生长素运输系统中诱导了生理不对称，并且钙增加了生长素在根中的总运输量。
