Pores;t;ology Management ELSEVIER Forest Ecology and Management 93 (I 997) 55-6 1 Photosynthetic response of Populus euphratica to salt stress Huan-Cheng Ma a, Lindsay Fung ‘, Sha-Sheng Wang ‘.*, Arie Altman b, Aloys Hiittermann ’ ’ Experimental Center of Forest Biology, Beijing Forestp Uniclersity. Beijing 100083, People’s Republic of Chino b The Otto Warburg Center for Agricultural Biotechnology, The Hebrew Unirersi@ of Jerusalem. Rehol!ot. Isruel ’ Forest Botanieai fnstitute, Giittingen Uniiwrsity, Gijttingen. German[v Accepted 20 September 1996 Abstract P. euphruticu Olive and the hybrids (P. tulassica Kom X (P. euphrutica + Sulix a/ha L)) seedlings were subjected to low (50mM NaCl) and high salt (200mM NaCI) treatments to determine their photosynthetic responses to salt stress. The photosynthetic pattern indicated that P. euphrutica is a C3 plant with a high CO, compensation point (150 kmol mol - ’ ) and saturation point (900 urn01 molt ’ 1, but has some characteristics of C4 plants with a high light saturation point (2800 p,mol rn-’ s-l> m control conditions. CO2 compensation and saturation pomts increased with high salt treatment for both the hybrid and f. euphruticu while light saturation point decreased with salt treatment. The net photosynthesis of P. euphraticn with high salt treatment declined in the first 14 days and recovered to 70% that with control in day 21 when soil salt content was about 0.7% NaCl, while that of the hybrids did not recover when soil salt content was about 0.5% NaCl with hgih salt treatment. With increasing salt levels, Chlorophyll a contents and Chlorophyll a/b ratio increased. while Chlorophyll b and carotenoid contents decreased by day 10, when photosynthesis was heavily depressed for both species. Fluorescence patterns confirmed that reduction of photosynthesis under high salt treatment was not due to damage of the photosynthetic apparatus, but more likely due to inhibition of the dark reaction. 0 1997 Elsevier Science B.V. Keywords; P. euphruticcl: Salt tolerance; Photosynthesis; Plant fluorescence; Populus 1. Introduction tion is 1560-3700mm in the area. The soil saliniza- Pnpuius euphratica Olive is one of two species in the Turanga section of Populus (Zheng, 1983). It is native to northwest China, middle and west Asia and some areasin Europe (Xu, 1988). Together with P. pruinosa, they are the only two tall tree species that exist and form forests in the desert area in Northwest China (Qin, 1959). The annual rainfall is less than 50mm (range: 1.9-257.55 mm> and annual evapora- tion hasbeen a severeproblem limiting the establish- ment of forest (Wang et al., 1995). Therefore, it is necessaryto test salt tolerance of P. euphruticu for the large scaleafforestation. The total salt content of soils where P. euphrutica forest grows is typically about 1 %, but can reach 7% (Liu and Huang, 1990; Qin, 1959; Wei, 1993). The timber of this species is widely used for house construction, fuelwood and farm tool manufacture. The species hasbeen particu- Corresponding author. larly used as a pioneer plant to stabilize sand dunes and form shelter belts to protect agriculture and 037% 1 f 27/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rghts reserved. PII S037R- I I27(96)03943-6