ABSTRACT
Combined effects of acid rain and lanthanum on growth of soybean seedling (Glycine max) and its inherent mechanism were studied in this paper. Compared with treatments by simulated acid rain (pH 3.0, 3.5, 4.5) or rare earth La(III) (60, 100 and 300 mg x L(-1)), the decrease degree of growth parameters in combined treatments was higher, indicating that there were a synergistic effects between acid rain and La. Moreover,the inhibition effects of acid rain and La(III) were more obvious when pH value of acid rain was lower or the concentration of La(III) was higher. The changes of photosynthetic parameters were similar to those of growth, but the decrease degree of each parameter was not same in the same treatment group. The decrease degree of optimal PSII photochemical efficiency (Fv/Fm) and chlorophyll content (Chl) were 9.35%-22.75% and 9.14%-24.53%, respectively, lower than that of photosynthetic rate Pn (22.78%-84.7%), Hill reaction rate (15.52%-73.38%) and Mg2+ -ATPase activity (14.51%-71.54%), showing that the sensitivity of photosynthetic parameters to the combined factors was different. Furthermore, relative analysis showed that the change of Pn were mainly affected by Hill reaction rate and Mg2+ -ATPase activity, and was less influenced by Chl and Fv/Fm. It indicates that the effect of acid rain and La on each reaction in photosynthesis was different, and the inhibition of combined treatments on photosynthesis in plants was one of the main factors affecting growth of plant.
