近日，中国科学院南京土壤研究所施卫明研究组在《Plant, Cell and Environment》（2009 IF 5.081）杂志发表文章，发现了NH₄⁺外流和GMPase的活性调节NH₄⁺抑制的根尖的生长。

       根在生长过程中对NH₄⁺非常敏感，过量的NH₄⁺阻碍根的生长和发育，这种抑制不依赖于生长素和乙烯的信号转导，使用非损伤微测技术发现高NH₄⁺处理后伸长区出现显著的NH₄⁺外流，这种外流在NH₄⁺超敏感的突变体vtc1-1中更显著，在GMPase的突变体中缺乏，因此，限制跨膜的NH₄⁺流和GMPase的功能能够显著降低拟南芥对NH₄⁺毒性的反应。
       这项工作为植物如何避免铵盐毒害提供了理论解释，对于理解其他非生物胁迫对根的生长发育的影响有非常重要的参考价值。
       这篇文章中的NH₄⁺流速的测定在旭月（北京）科技有限公司的测试中心完成。
       目前，非损伤微测技术能够直接测定植物的主要营养物质如K⁺、NH₄⁺和NO₃^-，这种活体测定技术是研究植物营养的最佳手段。

       关键词：NH₄⁺毒害，细胞伸长，流速，施卫明，非损伤微测技术，旭月

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Abstract：

Root growth in higher plants is sensitive to excess ammonium(NH₄⁺). Our study shows that contact of NH₄⁺ with the primary root tip is both necessary and sufficient to the
development of arrested root growth under NH₄⁺ nutrition in Arabidopsis. We show that cell elongation and not cell division is the principal target in the NH₄⁺ inhibition of primary root growth. Mutant and expression analyses using DR5:GUS revealed that the growth inhibition is furthermore independent of auxin and ethylene signalling. NH₄⁺fluxes along the primary root, measured using the Scanning Ion-selective Electrode Technique, revealed a significant stimulation of NH₄⁺ efflux at the elongation zone following treatment with elevated NH₄⁺, coincident with the inhibition of root elongation. Stimulation of NH₄⁺ efflux and inhibition of cell expansion were significantly more pronounced in the NH₄⁺-hypersensitive mutant vtc1-1, deficient in the enzyme GDP-mannose pyrophosphorylase (GMPase).We conclude that both restricted transmembrane NH₄⁺ fluxes and proper functioning of GMPase in roots are critical to minimizing the severity of the NH₄⁺ toxicity response in Arabidopsis.