Differential growth of plants in response to the changes in the light and gravity vectors requires a complex signal transduction cascade. Although many of the details of the mechanisms by which these differential growth responses are induced are as yet unknown, auxin has been implicated in both gravitropism and phototropism. Specifically, the redistribution of auxin across gravity or light-stimulated tissues has been detected and shown to be required for this process. The approaches by which auxin has been implicated in tropisms include isolation of mutants altered in auxin transport or response with altered gravitropic or phototropic response, identification of auxin gradients with radiolabeled auxin and auxin-inducible gene reporter systems, and by use of inhibitors of auxin transport that block gravitropism and phototropism. Proteins that transport auxin have been identified and the mechanisms which determine auxin transport polarity have been explored. In addition, recent evidence that reversible protein phosphorylation controls this process is summarized. Finally, the data in support of several hypotheses for mechanisms by which auxin transport could be differentially regulated during gravitropism are examined. Although many details of the mechanisms by which plants respond to gravity and light are not yet clear, numerous recent studies demonstrate the role of auxin in these processes.

中文翻译：

---

生长素和嗜性

响应光和重力矢量变化的植物差异生长需要复杂的信号转导级联。尽管诱导这些差异生长反应的机制的许多细节尚不清楚，但生长素与向地性和向光性有关。具体来说，生长素在重力或光刺激组织中的重新分布已被检测到，并且表明这是该过程所必需的。生长素与趋向性有关的方法包括分离生长素转运或响应改变的向重或向光性反应的突变体，用放射性标记的生长素和生长素诱导基因报告系统鉴定生长素梯度，以及使用生长素转运抑制剂阻止向地性和向光性。已经鉴定了运输生长素的蛋白质，并且已经探索了决定生长素运输极性的机制。此外，总结了可逆蛋白质磷酸化控制这一过程的最新证据。最后，研究了支持生长素转运在向地性过程中受到差异调节的机制的几个假设的数据。尽管植物对重力和光作出反应的机制的许多细节尚不清楚，但最近的许多研究证明了生长素在这些过程中的作用。研究了支持生长素转运在向地性过程中受到差异调节的机制的几个假设的数据。尽管植物对重力和光作出反应的机制的许多细节尚不清楚，但最近的许多研究证明了生长素在这些过程中的作用。研究了支持生长素转运在向地性过程中受到差异调节的机制的几个假设的数据。尽管植物对重力和光作出反应的机制的许多细节尚不清楚，但最近的许多研究证明了生长素在这些过程中的作用。