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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

NaCl-Induced Alternations of Cellular and Tissue Ion Fluxes in Roots of Salt-Resistant and Salt-Sensitive Poplar Species^{1,[C],[W],[OA]}

College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, People's Republic of China (J. Sun, S.C., S.D., R.W., N.L., X.S., X.Z., C.L.); Key Laboratory of Biological Resources Protection and Utilization in Hubei Province, Hubei University for Nationalities, Enshi 445000, People's Republic of China (S.C., X.Z.); Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China (Z.H.); and Xuyue (Beijing) Science and Technology Co., Ltd., Haidian District, Beijing 100080, People's Republic of China (Z.Z., J. Song, Y.X.)

Using the scanning ion-selective electrode technique, fluxes of H⁺, Na⁺, and Cl^– were investigated in roots and derived protoplasts of salt-tolerant Populus euphratica and salt-sensitive Populus popularis 35-44 (P. popularis). Compared to P. popularis, P. euphratica roots exhibited a higher capacity to extrude Na⁺ after a short-term exposure to 50 mM NaCl (24 h) and a long term in a saline environment of 100 mM NaCl (15 d). Root protoplasts, isolated from the long-term-stressed P. euphratica roots, had an enhanced Na⁺ efflux and a correspondingly increased H⁺ influx, especially at an acidic pH of 5.5. However, the NaCl-induced Na⁺/H⁺ exchange in root tissues and cells was inhibited by amiloride (a Na⁺/H⁺ antiporter inhibitor) or sodium orthovanadate (a plasma membrane H⁺-ATPase inhibitor). These results indicate that the Na⁺ extrusion in stressed P. euphratica roots is the result of an active Na⁺/H⁺ antiport across the plasma membrane. In comparison, the Na⁺/H⁺ antiport system in salt-stressed P. popularis roots was insufficient to exclude Na⁺ at both the tissue and cellular levels. Moreover, salt-treated P. euphratica roots retained a higher capacity for Cl^– exclusion than P. popularis, especially during a long term in high salinity. The pattern of NaCl-induced fluxes of H⁺, Na⁺, and Cl^– differs from that caused by isomotic mannitol in P. euphratica roots, suggesting that NaCl-induced alternations of root ion fluxes are mainly the result of ion-specific effects.

² Present address: Tianjin Landscape-gardening Institute, Tianjin 300181, China.

³ Present address: The Centre for Research Ecotoxicology and Environmental Remediation, Institute of Agricultural Environmental Protection, Ministry of Agriculture, Tianjin 300191, China.

The author responsible for the distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Shaoliang Chen (lschen{at}bjfu.edu.cn).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

^[OA] Open access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.129494

^* Corresponding author; e-mail lschen{at}bjfu.edu.cn.

Received September 7, 2008; accepted November 18, 2008; published November 21, 2008.

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