Takahashi Hideyuki, Miyazawa Yutaka, Fujii Nobuharu
Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
Plant Mol Biol. 2009 Mar;69(4):489-502. doi: 10.1007/s11103-008-9438-x. Epub 2008 Dec 16.
Terrestrial plants have evolved remarkable morphological plasticity that enables them to adapt to their surroundings. One of the most important traits that plants have acquired is the ability to sense environmental cues and use them as a basis for governing their growth orientation. The directional growth of plant organs relative to the direction of environmental stimuli is a tropism. The Cholodny-Went theory proposes that auxin plays a key role in several tropisms. Recent molecular genetic studies have strongly supported this hypothesis for gravitropism. However, the molecular mechanisms of other tropisms are far less clear. Hydrotropism is the response of roots to a moisture gradient. Since its re-discovery in 1985, root hydrotropism has been shown to be common among higher plant species. Additionally, in some species, gravitropism interferes with hydrotropism, suggesting that both shared and divergent mechanisms mediating the two tropisms exist. This hypothesis has been supported by recent studies, which provide an understanding of how roots sense multiple environmental cues and exhibit different tropic responses. In this review, we focus on the overlapping and unique mechanisms of the hormonal regulation underlying gravitropism and hydrotropism in roots.
陆生植物进化出了显著的形态可塑性，使它们能够适应周围环境。植物获得的最重要特征之一是感知环境线索并将其作为控制生长方向基础的能力。植物器官相对于环境刺激方向的定向生长是一种向性运动。 Cholodny-Went理论提出，生长素在几种向性运动中起关键作用。最近的分子遗传学研究有力地支持了这一关于向重力性的假说。然而，其他向性运动的分子机制还远不清楚。向水性是根对水分梯度的反应。自1985年重新发现以来，根的向水性已在高等植物物种中普遍存在。此外，在一些物种中，向重力性会干扰向水性，这表明介导这两种向性运动的机制既有共同之处，也有不同之处。这一假说得到了最近研究的支持，这些研究有助于理解根如何感知多种环境线索并表现出不同的向性反应。在这篇综述中，我们重点关注根中向重力性和向水性背后激素调节的重叠和独特机制。
