Plant Ecophysiology , Institute of Environmental Biology , Utrecht University , Padualaan 8, 3584 CH Utrecht , The Netherlands.
AoB Plants. 2011;2011:plr031. doi: 10.1093/aobpla/plr031. Epub 2011 Dec 12.
Many plant species can actively reorient their organs in response to dynamic environmental conditions. Organ movement can be an integral part of plant development or can occur in response to unfavourable external circumstances. These active reactions take place with or without a directional stimulus and can be driven either by changes in turgor pressure or by asymmetric growth. Petiole hyponasty is upward movement driven by a higher rate of cell expansion on the lower (abaxial) compared with the upper (adaxial) side. Hyponasty is common among rosette species facing environmental stresses such as flooding, proximity of neighbours or elevated ambient temperature. The complex regulatory mechanism of hyponasty involves activation of pathways at molecular and developmental levels, with ethylene playing a crucial role.
We present current knowledge on the mechanisms that promote hyponasty in the context of other organ movements, including tropic and nastic reactions together with circumnutation. We describe major environmental cues resulting in hyponasty and briefly discuss their perception and signal transduction. Since ethylene is a central agent triggering hyponasty, we focus on ethylene in controlling different stages during plant development and summarize current knowledge on the relationship between ethylene and cell growth.
许多植物物种可以主动调整器官方向以适应动态环境条件。器官运动可以是植物发育的一个组成部分，也可以是对不利外部环境的反应。这些主动反应可以在有或没有方向刺激的情况下发生，并且可以由膨压变化或不对称生长驱动。叶柄下弯是由下（远轴）侧比上（近轴）侧细胞扩展速度更高驱动的向上运动。下弯在面临环境压力（如洪水、邻近植物或环境温度升高）的莲座丛物种中很常见。下弯的复杂调控机制涉及分子和发育水平上途径的激活，其中乙烯起着关键作用。
我们介绍了在其他器官运动（包括向性和感性反应以及回旋运动）背景下促进下弯的机制的最新知识。我们描述了导致下弯的主要环境线索，并简要讨论了它们的感知和信号转导。由于乙烯是触发下弯的中心物质，我们专注于乙烯在控制植物发育的不同阶段，并总结了当前关于乙烯与细胞生长之间关系的知识。
