背景回顾：Efficient foraging by plant roots relies on the ability to sense multiple physical and chemical cues in soil and to reorient growth accordingly (tropism). Root tropisms range from sensing gravity (gravitropism), light (phototropism), water (hydrotropism), touch (thigmotropism), and more. Electrotropism, also known as galvanotropism, is the phenomenon of aligning growth with external electric fields and currents. 

提出问题：Although root electrotropism has been observed in a few species since the end of the 19^th century, its molecular and physical mechanisms remain elusive, limiting its comparison with the more well-defined sensing pathways in plants. 

结果1：Here we provide a quantitative and molecular characterization of root electrotropism in the model system Arabidopsis (Arabidopsis thaliana), showing that it does not depend on an asymmetric distribution of the plant hormone auxin, but instead requires the biosynthesis of a second hormone, cytokinin. 

结果2：We also show that the dose-response kinetics of the early steps of root electrotropism follows a power law analogous to the one observed in some physiological reactions in animals. 

展望：Future studies involving more extensive molecular and quantitative characterization of root electrotropism would represent a step towards a better understanding of signal integration in plants and would also serve as an independent outgroup for comparative analysis of electroreception in animals and fungi.

 摘 要 

植物的根在土壤中的高效搜寻主要依赖于其对土壤中多种理化信号的感知能力，并相应地调整生长方向，即所谓的向性生长。根的向性包括感知重力（向重力性）、光（向光性）、水（向水性）、触摸（向触性）等。向电性，是指将生长与外部电场和电流方向相一致的现象。尽管自19世纪末以来，在少数物种中观察到了根的向电性，但其分子和物理机制仍难以捉摸，限制了其与植物中其它确切的感应途径作比较。本文中，作者以拟南芥为模式系统，对其根的向电性进行了定量和分子特征研究，发现拟南芥根的向电性并不依赖于植物激素生长素的不对称分布，反而是需要另外一种植物激素细胞分裂素的生物合成。作者的研究还表明，根电向性早期阶段的剂量响应动力学遵循幂律，类似于在动物的某些生理反应中所观察到的幂律。未来对于植物根的向电性研究会更加广泛，这将有助于我们更好地理解植物信号整合，也将成为动物和真菌电感知之外的另一个独立研究方向。