Dedolph R R, Naqvi S M, Gordon S A
Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois.
Plant Physiol. 1966 May;41(5):897-902. doi: 10.1104/pp.41.5.897.
Oat seedlings were grown in a sand medium on clinostats with horizontal axes of rotation to nullify the directional component of the gravity-force vector. Coleoptile segments from such seedlings showed an enhanced absorption of apically applied exogenous auxin (indole-3-acetic acid), compared to segments from vertically rotated or stationary controls. Absorption of basally applied auxin and auxin transport were unaffected by the gravity treatments. Horizontal rotation did not materially change the amount of auxin produced and transported from excised coleoptile tips: however, plants so rotated showed an enhanced curvature response to unilaterally applied auxin.Collectively, these experiments indicate that enhanced plant responses to horizontal clinostat rotation, where rates of rotation are sufficient to nullify the directional component of the gravity-force vector, are caused primarily by increases in metabolism and not by a modification of auxin availability. These data do not support recently advanced hypotheses that the polarity of auxin transport is based on gravitational sedimentation of cell inclusions.
燕麦幼苗种植在带有水平旋转轴的回转器的沙子培养基中，以消除重力矢量的方向分量。与垂直旋转或固定对照的幼苗的胚芽鞘切段相比，此类幼苗的胚芽鞘切段对顶端施加的外源生长素（吲哚 - 3 - 乙酸）的吸收增强。基部施加生长素的吸收和生长素运输不受重力处理的影响。水平旋转并未实质性改变从切除的胚芽鞘尖端产生和运输的生长素的量：然而，如此旋转的植物对单侧施加的生长素表现出增强的弯曲反应。总体而言，这些实验表明，当旋转速率足以消除重力矢量的方向分量时，植物对水平回转器旋转的增强反应主要是由代谢增加引起的，而不是由生长素可用性的改变引起的。这些数据不支持最近提出的关于生长素运输极性基于细胞内含物重力沉降的假说。
