Abstract: The heavy saline-alkali land in the Songnen plain of NE China was selected as the control(pH,10.15; EC,1 220 μscm^-1; soil compaction degree,2 199 kPa）and adjacent saline-alkali land after soil amelioration(pH,9.17; EC, 388 μscm^-1; soil compaction degree,1 170 kPa) was selected as treatment site.3-yr-old Yinzhong poplar(Populus alba×P.berolinensis) grown in these two sites over 1 year were analyzed and we found that: 1) chlorophyll a+b, chl.a/b and total carotenoids of the leaf in ameliorated soil were much higher than those in the untreated saline-alkali soil, while the differences in stem bark and branch were far smaller than those in the leaf; 2) All the three C₄ enzymes expressed at a basis of fresh weight showed small differences among leaf, branch and stem bark, and the influences from saline-alkali soil amelioration treatment were rather slight; 3) When the unit was expressed as chlorophyll basis, significant differences among different organs as well as between two soil treatments were observed, i.e., PEPC in stem bark and branch was respectively 4.4 fold and 3.1 fold higher than those in leaf in the untreated control, while these differences became 8.6 fold and 2.6 fold in the ameliorated soil treatment. In the untreated control land, NADP-ME in stem bark and branch were 1.7 fold and 2.1 fold higher than those in leaf, while these difference became 17.6 fold and 6.4 fold in the ameliorated soil treatment. Similarly, NADP-MDH in stem bark and branch in the untreated saline-alkali land were respectively 1.7 fold and 1.4 fold higher than those in leaf, while they became 6.4 fold and 13.7 fold in the ameliorated soil treatment. Our findings manifest that non-photosynthetic organs (such as stem and branch) had much higher content of C₄ pathway-related enzymes comparing with the leaf lamina. Moreover, such differences could be adjusted by soil saline-alkali degree, i.e. the differences could be dramatically enlarged in the ameliorated saline-alkali land. Possibly, the changes in C₄-related enzymes might be effective physiological paramenters for evaluating plant acclimation to saline-alkali soil.

Key words: PEPC, NADP-MDH, NADP-ME, chlorophyll, non-photosynthetic organs