Department of Biological Sciences, University of Alberta, Edmonton Alberta, Canada, T6G 2E9.
J Integr Plant Biol. 2013 Sep;55(9):824-34. doi: 10.1111/jipb.12086.
Plant vascular cells are joined end to end along uninterrupted lines to connect shoot organs with roots; vascular strands are thus polar, continuous, and internally aligned. What controls the formation of vascular strands with these properties? The "auxin canalization hypothesis"-based on positive feedback between auxin flow through a cell and the cell's capacity for auxin transport-predicts the selection of continuous files of cells that transport auxin polarly, thus accounting for the polarity and continuity of vascular strands. By contrast, polar, continuous auxin transport-though required-is insufficient to promote internal alignment of vascular strands, implicating additional factors. The auxin canalization hypothesis was derived from the response of mature tissue to auxin application but is consistent with molecular and cellular events in embryo axis formation and shoot organ development. Objections to the hypothesis have been raised based on vascular organizations in callus tissue and shoot organs but seem unsupported by available evidence. Other objections call instead for further research; yet the inductive and orienting influence of auxin on continuous vascular differentiation remains unique.
植物的维管细胞沿着不间断的线连接在一起，将芽器官与根连接起来；因此，维管束是极性的、连续的和内部对齐的。是什么控制着具有这些特性的维管束的形成？基于生长素流经细胞和细胞生长素运输能力之间的正反馈的“生长素通道化假说”，预测了连续的细胞文件的选择，这些细胞极性地运输生长素，从而解释了维管束的极性和连续性。相比之下，尽管极性、连续的生长素运输是必需的，但不足以促进维管束的内部对齐，这暗示了其他因素的作用。生长素通道化假说源于成熟组织对生长素应用的反应，但与胚胎轴形成和芽器官发育中的分子和细胞事件一致。基于愈伤组织和芽器官中的维管组织对该假说提出了反对意见，但似乎没有现有证据支持。其他反对意见则呼吁进一步研究；然而，生长素对连续血管分化的诱导和定向影响仍然是独特的。
