题目
在顶端优势现象中，侧芽生长素浓度总是高于顶芽，但是顶芽产生的生长素仍大量积存于侧芽部位，这种生长素极性运输的特性是因为生长素的运输方式属于 A.自由扩散 Ｂ.渗透作用 Ｃ.协助扩散 Ｄ.主动运输
答案：D 解析: 略
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