Effects of NaCl on shoot growth, transpiration, ion compartmentation, and transport in regenerated plants of Populus euphratica and Populus tomentosa Shaoliang Chen, Jinke Li, Shasheng Wang, Eberhard Fritz, Aloys Hüttermann, and Arie Altman Abstract: The effect of a 20-day NaCl treatment on shoot growth, transpiration, ion uptake and transport, and intracellular ion compartmentation was investigated in regenerated plants of Populus euphratica Oliv. and Populus tomentosa Carr. Plants watered with 100 mM NaCl for 8 days and then 200 mM NaCl for 12 days exhibited soil NaCl concentrations of 60 and 95 mM, respectively. Unit transpiration rates and relative growth rates of P. tomentosa were restricted more by salinity as compared with P. euphratica. Salinized P. tomentosa exhibited leaf necrosis whereas no damage was seen in stressed P. euphratica. Compared with P. tomentosa, P. euphratica had considerably lower rates of net root uptake and transport of salt ions (Na + and Cl – ) to the shoots under salinity. The relatively lower unit transpira- tion rates of P. euphratica and the lower salt concentrations in the xylem of salinized P. euphratica contribute to its greater capacity for salt exclusion. X-ray microanalysis showed that P. euphratica had a greater ability to restrict radial salt transport in roots by blocking apoplasmic salt transport and sequestering more Cl – in cortical vacuoles. In addition, P. euphratica maintained higher K + uptake and transport than P. tomentosa in the presence of high external Na + con- centrations. Résumé : L’effet d’un traitement au NaCl appliqué pendant 20 jours sur la croissance des pousses, la transpiration, l’absorption et le transport des ions et le compartimentage intracellulaire des ions a été étudié sur des plants régénérés de Populus euphratica Oliv. et Populus tomentosa Carr. Les plants arrosés avec 100 mM de NaCl pendant 8 jours et par la suite avec 200 mM de NaCl pendant 12 jours avaient des concentrations de NaCl dans le sol de respectivement 60 et 95 mM. Le taux de transpiration unitaire et le taux de croissance relative de P . tomentosa étaient davantage inhi- bés par la salinité comparativement à P . euphratica. L’exposition au sel a provoqué des nécroses foliaires chez P . to- mentosa mais non chez P . euphratica. Comparativement à P . tomentosa, P . euphratica avait des taux d’absorption racinaire nette et de transport des ions de sel (Na + et Cl – ) vers les pousses considérablement plus faibles en conditions de salinité. Le taux de transpiration unitaire et la concentration de sel dans le xylème relativement plus faibles chez P . euphratica exposé au sel contribuent à sa plus grande capacité d’exclure le sel. Des analyses microscopiques aux rayons X montrent que P . euphratica peut mieux restreindre le transport radial du sel dans les racines en bloquant le transport du sel dans l’apoplasme et en séquestrant plus de Cl – dans les vacuoles des cellules corticales. De plus, P . euphratica absorbe et transporte plus de K + que P . tomentosa en présence de concentrations élevées de Na + dans le mi- lieu externe. [Traduit par la Rédaction] Chen et al. 975 Introduction Genotypic differences in salinity tolerance within the ge- nus Populus have been reported in recent years (Ma et al. 1997; Fung et al. 1998a, 1998b; Chen et al. 2001). Compar- ative investigations have shown that Populus euphratica Oliv. is more salt resistant than its hybrid Populus talassica Kom. × (P. euphratica + Salix alba L.) and other genotypes (e.g., Populus deltoides × P. nigra (Dode) Guinier cv. I-214, Populus simonii × (P. pyramidalis × Salix matsudana) Populus popularis cv. 35-44) (Ma et al. 1997; Fung et al. 1998b; Chen et al. 2001). Salt tolerance of P. euphratica has been attributed mainly to its greater ability to exclude salt (Chen et al. 2001). Within the roots, ion compartmentation and development of protective barriers (e.g., Casparian bands) are likely to play a role in salt exclusion. Intra- specific differences in the ability for salt exclusion have been attributed to early formation of Casparian bands, which block apoplasmic ion transport (Thomson 1988). Jeschke (1984) found that Na + compartmentation in root vacuoles of barley lowered its transport to the shoot. Thus, it may be in- Can. J. For. Res. 33: 967–975 (2003) doi: 10.1139/X03-066 © 2003 NRC Canada 967 Received 13 June 2001. Accepted 20 February 2003. Published on the NRC Research Press Web site at http://cjfr.nrc.ca on 28 April 2003. S. Chen, 1 J. Li, and S. Wang. Experimental Centre of Forest Biology, P.O. Box 162, Beijing Forestry University, Beijing, 100083, People’s Republic of China. E. Fritz and A. Hüttermann. Forstbotanisches Institut, Universität Göttingen, Büsgenweg 2, 37077, Göttingen, Germany. A. Altman. Faculty of Agricultural Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76-100, Israel. 1 Corresponding author: (e-mail: Lschen@bjfu.edu.cn).