The Impact Of Simulated Acid Rain On Physiological And Ecological Characteristics Of Eucommia

Effect of simulated acid rain on eec-physiological characteristics of Eucommia ulmoides in the spring, summer and autumn were studied in this research in which seven groups of simulated acid rain including pH5.O,4.5,4.O,3.5,3.O,2.Sand an extra controlled pH of 5.6(CK) were designed and Eucommia ulmoides seedlings cultivated in pots with purple soil were used as experimental materials. Under the stress of simulated acid rain experimental results at first showed that the pH value of soil in the spring and summer had no more change but in autumn changed greatly and in autumn the toxic effects of aluminiumon on the roots did not take place except for the group of p142.5. On the other hand, the contents of K+, Ca2+ and the pH value of leaf cell in leaves decreased with delined pH value of acid rain and were positively correlated with it in the spring,summer and autumn. The increase of the MDA content and the permeability of membrane lipid peroxidation became more serious with the time past and the precipitation of acid rain increased in the sring, summer and autumn. However, the change of the activity about protective enzyme SOD, CAT, POD and the content about antioxideant AsA were sole peak curve in the spring and summer but in the autumn they were positively correlated with the pH value of acid rain, at the same time, the content of Pro were negatively correlated with it in the spring, summer and autumn. These results showed that Eucommia ulmoides had resistance and adaptability to the stress of smulated acid rain to a certain degree. The activity of some key enzymes in N-metabolism and the contents of some correlativesubstances in Eucommia ulmoides leaves were studied in this research. It was found that under a certain pH value of simulated acid rain stress the activity of NR, OS , GDH and GPT decreased in the spring, summer and autumn with declined pH value of acid rain , and the decreasing rate of these enzymes increased with the spring, summer and autumn past. It was also found that in the spring, summer and autumn the contents of soluble protein and total nitrogen decreased with declined pH value of acid rain(the contents of soluble protein in the summer and autumn were positively correlated with the pH value of acid rain),but the contents of total free amine acid in the spring, summer and autumn increased with declined pH value of acid rain(they were correlated with the pH value of acid rain significantly in the spring and summer and ever more in the autumn). Under the stress of simulated acid rain in the spring, summer and autumn, the CO2 compensation points and the light compensation points of Eucommia ulmo ides heightened but the light saturation and the net photosynthetic rate dropped, and with the precipitation of acid rain increased and the stress time prolonged, they increased or dropped greatly. Furthermore, the chlorophll content ,the ratio of Chl alChl b and the activity of Hill Reaction decreased under the stress of a certain pH value of acid rain in the spring, summer and autumn and were all positively correlated with the pH value of acid rain. These resultes indicated that the simulated acid rain had significant effects on photosynthetic physiological characteristics of Eucommia ulmo ides. The growth indexes such as the fresh or dry weight of roots, stems and leaves, the leaf area and height were examined in the spring, summer and autumn. It indicated that the growth of Eucommia ulmo ides was restrained by pH 3.0 or under pH3.0 acid rain in the spring and summer and pH 3.5 or under pH3.5 acid rain in the...