近日，中國科學院南京土壤研究所施衛(wèi)明研究組在《Plant, Cell and Environment》（2009 IF 5.081）雜志發(fā)表文章，發(fā)現(xiàn)了NH₄⁺外流和GMPase的活性調節(jié)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(fā)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(fā)現(xiàn)高NH₄⁺處理后伸長區(qū)出現(xiàn)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(fā)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(yǎng)物質如K⁺、NH₄⁺和NO₃^-，這種活體測定技術是研究植物營養(yǎng)的最佳手段。

       關鍵詞：NH₄⁺毒害，細胞伸長，流速，施衛(wèi)明，非損傷微測技術，旭月

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.