Sun Jian, Dai Songxiang, Wang Ruigang, Chen Shaoliang, Li Niya, Zhou Xiaoyang, Lu Cunfu, Shen Xin, Zheng Xiaojiang, Hu Zanmin, Zhang Zengkai, Song Jin, Xu Yue
College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, P.R. China.
Tree Physiol. 2009 Sep;29(9):1175-86. doi: 10.1093/treephys/tpp048. Epub 2009 Jul 28.
Using the non-invasively ion-selective microelectrode technique, flux profiles of K(+), Na(+) and H(+) in mature roots and apical regions, and the effects of Ca(2+) on ion fluxes were investigated in salt-tolerant poplar species, Populus euphratica Oliver and salt-sensitive Populus simonii x (P. pyramidalis + Salix matsudana) (Populus popularis 35-44, P. popularis). Compared to P. popularis, P. euphratica roots exhibited a greater capacity to retain K(+) after exposure to a salt shock (SS, 100 mM NaCl) and a long-term (LT) salinity (50 mM NaCl, 3 weeks). Salt shock-induced K(+) efflux in the two species was markedly restricted by K(+) channel blocker, tetraethylammonium chloride, but enhanced by sodium orthovanadate, the inhibitor of plasma membrane (PM) H(+)-ATPase, suggesting that the K(+) efflux is mediated by depolarization-activated (DA) channels, e.g., KORCs (outward rectifying K(+) channels) and NSCCs (non-selective cation channels). Populus euphratica roots were more effective to exclude Na(+) than P. popularis in an LT experiment, resulting from the Na(+)/H(+) antiport across the PM. Moreover, pharmacological evidence implies that the greater ability to control K(+)/Na(+) homeostasis in salinized P. euphratica roots is associated with the higher H(+)-pumping activity, which provides an electrochemical H(+) gradient for Na(+)/H(+) exchange and simultaneously decreases the NaCl-induced depolarization of PM, thus reducing Na(+) influx via NSCCs and K(+) efflux through DA-KORCs and DA-NSCCs. Ca(2+) application markedly limited salt-induced K(+) efflux but enhanced the apparent Na(+) efflux, thus enabling the two species, especially the salt-sensitive poplar, to retain K(+)/Na(+) homeostasis in roots exposed to prolonged NaCl treatment.
利用非侵入性离子选择性微电极技术，研究了耐盐杨树品种胡杨（Populus euphratica Oliver）和盐敏感杨树品种小叶杨×（新疆杨 + 旱柳）（群众杨35 - 44，群众杨）成熟根和根尖区域中钾离子（K⁺）、钠离子（Na⁺）和氢离子（H⁺）的通量分布，以及钙离子（Ca²⁺）对离子通量的影响。与群众杨相比，胡杨根在受到盐冲击（SS，100 mM NaCl）和长期（LT）盐胁迫（50 mM NaCl，3周）后表现出更强的钾离子保留能力。钾离子通道阻滞剂氯化四乙铵显著抑制了两种杨树品种盐冲击诱导的钾离子外流，但质膜（PM）H⁺ - ATP酶抑制剂原钒酸钠增强了钾离子外流，这表明钾离子外流是由去极化激活（DA）通道介导的，例如外向整流钾离子通道（KORCs）和非选择性阳离子通道（NSCCs）。在长期实验中，胡杨根比群众杨更有效地排除钠离子，这是由于质膜上的Na⁺/H⁺逆向转运。此外，药理学证据表明，盐化胡杨根中控制K⁺/Na⁺稳态的更强能力与更高的H⁺泵浦活性有关，这为Na⁺/H⁺交换提供了电化学H⁺梯度，同时降低了NaCl诱导的质膜去极化，从而减少了通过NSCCs的钠离子内流以及通过DA - KORCs和DA - NSCCs的钾离子外流。施用钙离子显著限制了盐诱导的钾离子外流，但增强了表观钠离子外流，从而使这两个品种，特别是盐敏感杨树，在长期NaCl处理的根中维持K⁺/Na⁺稳态。
