近日，中國科學院南京土壤研究所施衛明研究組在《Plant, Cell and Environment》（2009 IF 5.081）雜志發表文章，發現了NH₄⁺外流和GMPase的活性調節NH₄⁺抑制的根尖的生長。

       根在生長過程中對NH₄⁺非常敏感，過量的NH₄⁺阻礙根的生長和發育，這種抑制不依賴于生長素和乙烯的信號轉導，使用非損傷微測技術發現高NH₄⁺處理后伸長區出現顯著的NH₄⁺外流，這種外流在NH₄⁺超敏感的突變體vtc1-1中更顯著，在GMPase的突變體中缺乏，因此，限制跨膜的NH₄⁺流和GMPase的功能能夠顯著降低擬南芥對NH₄⁺毒性的反應。
       這項工作為植物如何避免銨鹽毒害提供了理論解釋，對于理解其他非生物脅迫對根的生長發育的影響有非常重要的參考價值。
       這篇文章中的NH₄⁺流速的測定在旭月（北京）科技有限公司的測試中心完成。
       目前，非損傷微測技術能夠直接測定植物的主要營養物質如K⁺、NH₄⁺和NO₃^-，這種活體測定技術是研究植物營養的最佳手段。

       關鍵詞：NH₄⁺毒害，細胞伸長，流速，施衛明，非損傷微測技術，旭月

施衛明老師簡介
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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.