Hasenstein K H, Evans M L
Botany Department, Ohio State University, Columbus 43210, USA.
Plant Physiol. 1988;86(3):890-4. doi: 10.1104/pp.86.3.890.
We examined the influence of aluminum and calcium (and certain other cations) on hormone transport in corn roots. When aluminum was applied unilaterally to the caps of 15 mm apical root sections the roots curved strongly away from the aluminum. When aluminum was applied unilaterally to the cap and 3H-indole-3-acetic acid was applied to the basal cut surface twice as much radioactivity (assumed to be IAA) accumulated on the concave side of the curved root as on the convex side. Auxin transport in the apical region of intact roots was preferentially basipetal, with a polarity (basipetal transport divided by acropetal transport) of 6.3. In decapped 5 mm apical root segments, auxin transport was acropetally polar (polarity = 0.63). Application of aluminum to the root cap strongly promoted acropetal transport of auxin reducing polarity from 6.3 to 2.1. Application of calcium to the root cap enhanced basipetal movement of auxin, increasing polarity from 6.3 to 7.6. Application of the calcium chelator, ethylene-glycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid, greatly decreased basipetal auxin movement, reducing polarity from 6.3 to 3.7. Transport of label after application of tritiated abscisic acid showed no polarity and was not affected by calcium or aluminum. The results indicate that the root cap is particularly important in maintaining basipetal polarity of auxin transport in primary roots of corn. The induction of root curvature by unilateral application of aluminum or calcium to root caps is likely to result from localized effects of these ions on auxin transport. The findings are discussed relative to the possible role of calcium redistribution in the gravitropic curvature of roots and the possibility of calmodulin involvement in the action of calcium and aluminum on auxin transport.
我们研究了铝和钙（以及某些其他阳离子）对玉米根中激素运输的影响。当将铝单侧施加到15毫米根尖切段的根冠上时，根会强烈地向远离铝的方向弯曲。当将铝单侧施加到根冠上，同时将³H-吲哚-3-乙酸施加到基部切割表面时，在弯曲根的凹侧积累的放射性（假定为吲哚-3-乙酸）是凸侧的两倍。完整根根尖区域的生长素运输优先向基部，极性（向基部运输除以向顶部运输）为6.3。在去除根冠的5毫米根尖切段中，生长素运输是向顶部极性的（极性 = 0.63）。将铝施加到根冠上强烈促进了生长素的向顶部运输，使极性从6.3降低到2.1。将钙施加到根冠上增强了生长素的向基部移动，使极性从6.3增加到7.6。施加钙螯合剂乙二醇双（β-氨基乙基醚）-N,N,N',N'-四乙酸，极大地降低了生长素的向基部移动，使极性从6.3降低到3.7。施加氚标记的脱落酸后标记物的运输没有极性，并且不受钙或铝的影响。结果表明，根冠在维持玉米初生根中生长素运输的向基部极性方面特别重要。通过将铝或钙单侧施加到根冠上诱导根弯曲，可能是这些离子对生长素运输的局部作用导致的。相对于钙重新分布在根的向重力性弯曲中的可能作用以及钙调蛋白参与钙和铝对生长素运输作用的可能性，对这些发现进行了讨论。
