| This paper studied the photo-synthesis characteristics of Ligustrum Lucidum Ait, Platanus hispanica and Pterocarya stenoptera and its physiological determinations responding to the air pollution, still studied the decontamination capability of the commom urban trees at the same time to the powder dust, sulfur dioxide and heavy metals inside the atmosphere, the results showed as follow: (1)The Vegetative photosynthesis was different along with seasonal changes .the daily course of net photosynthetic rate (Pn) and dark respiration rate (Rd) in early growing season and late growing season among three trees was single peaked ,which during fast growing season was double peaked. The daily course of transpiration rate (Tr) in Pterocarya stenoptera in June was double peaked, the rests were single peaked. The daily course of water use efficiency (WUE) among tree species was single peaked in April , and double peaked in June , but were little different . The seasonal change of Pn and Tr above three trees was the biggest during fast growing season, and smaller in early growing season and late growing season. The seasonal change of WUE was the lowest in summer , and higher in Spring and Autumn. The seasonal change of Rd was lowering progressively from early growing season to late growing season (2) Main factors affecting photosynthesis were continuously changing with season. These factors were humidity, temperature and vapor pressure deficit(VPD) in early growing season, in fast growing period temperature and vapor pressure deficit, in late growing season( September) temperature, light intensity and inter-cellular CO2 concentration(Ci), and in late growing phase( October) conductance to stomata(Cond) and light intensity. Tr was controlled by humidity, temperature and light intensity which affected Cond and VPD. Main factor affecting WUE and Rd was temperature, the other factors also had some influences. (3)Under air-polluted condition Pn, Ci , Cond , WUF ,Tr, the content of chlorophyll and soluble sugar in the three tree leaves all were less than those in clear settings , meanwhile VPD, membrane leakage,. Chlorophylla/b, free proline and malondialdehyde(MDA) showed the increasing tendency, and the increasing or decreasing range was different because of different plants and seasons (4) The content of chlorophyll, cell membrane conductance , free proline ,soluble sugar and MDA in leaves had different laws of seasonal variation. The Content of the sulfur in leaves showed the sharply negative correlation with chlorophyll, soluble sugar, showed the obviously positive correlation with cell membrane conductance and MDA , and the relationship with free praline did not attain to the apparent level . (5) Among different trees there existed a sharply difference. Absorbing dust capability on the bush leaves per unit was bigger than evergreen tall tree and defoliation tall tree. The dynamically seasonal regulation of absorbing dust capability of most green tree species in the same location was what is higher in spring and autumn, and what was lower in summer. (6) The amount of sulfur in different trees had obvious difference. The Content of the sulfur in the leaves of Ligustrum Lucidum, Cinnamomum camphora, Pterocarya stenoptera,, Liquidambar formosana and Cedrus deodara was what was higher in spring , lower in summer, and higher in the autumn, by contrast, the seasonally changing regulation of sulfur content of Platanus hispanica was going up from spring to autumn gradually . the amount of dust removal on existed the sharply positive correlation with sulfur content of leaves. The sulfur amount of the leaves presented a certain relativity to the distance from the pollution source. (7)The content of heavy metals element in different plants was different. The absorbing dust capability also existed apparent correlation with the variation of the lead and zinc content between natural leaves and not-washed leaves.
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