Gravitropism is directed growth of a plant or plant organ in response to gravity and can be divided into the following temporal sequence: perception, transduction, and response. This article is a review of the research on the early events of gravitropism (i.e., phenomena associated with the perception and transduction phases). The two major hypotheses for graviperception are the protoplast-pressure and starch-statolith models. While most researchers support the concept of statoliths, there are suggestions that plants have multiple mechanisms of perception. Evidence supports the hypothesis that the actin cytoskeleton is involved in graviperception/ transduction, but the details of these mechanisms remain elusive. A number of recent developments, such as increased use of the molecular genetic approach, magnetophoresis, and laser ablation, have facilitated research in graviperception and have allowed for refinement of the current models. In addition, the entire continuum of acceleration forces from hypo- to hyper-gravity have been useful in studying perception mechanisms. Future interdisciplinary molecular approaches and the availability of sophisticated laboratories on the International Space Station should help to develop new insights into mechanisms of gravitropism in plants.

中文翻译：

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植物向地性早期的机制

向地性是植物或植物器官响应重力的定向生长，可分为以下时间序列：感知、转导和响应。本文是对向地性早期事件（即与感知和转导阶段相关的现象）的研究的综述。重力感知的两个主要假设是原生质体压力和淀粉-静石模型。虽然大多数研究人员支持 statoliths 的概念，但也有人认为植物具有多种感知机制。证据支持肌动蛋白细胞骨架参与重力感知/转导的假设，但这些机制的细节仍然难以捉摸。最近的一些发展，例如分子遗传方法、磁泳和激光消融的使用增加，促进了重力感知的研究，并允许对当前模型进行改进。此外，从低重力到超重力的加速力的整个连续体在研究感知机制方面很有用。未来的跨学科分子方法和国际空间站上复杂实验室的可用性应该有助于对植物向地性机制的新见解。