The Characteristics And Influence Mechanism Of Stable Carbon Isotope Compositions Of Plant In Lan Zhou City

After rapid development and widely use in recent thirty years,the carbon isotope technique of plant,as an innovation,is applied to analyze the characteristics of stable carbon isotope composition and to reveal the changes of the external environmental factors.Light intensity,precipitation,temperature,and the concentration of atmospheric sulfur dioxide and nitrogen dioxide change the stomatal conduntance and photosynthetic carboxylase activity of the leaves to influnce the stable carbon isotope composition of the plant.The stable carbon isotope technique of plant as a new arisen monitoring technology can use to monitor the atmospheric pollutants such as sulfur dioxide and nitrogen dioxide, throught combining with the other monitoring index,and record the air pollution accurately and provide theoretical basis for the selection of resistant variety.The thesis analysis the stable carbon isotope composition characteristics of different organs(leaves,branches,trunks,roots) of Sophora japonica of Lan Zhou City to reveal the external environmental factors(intensity and the atmospheric pollution of sulfur dioxide and nitrogen dioxide) for the influence mechanism of stable carbon isotope composition of urban plant.Results are as follows:1) Theδ¹³C values of upper layer leaves of various sampling points are positive than middle layer.The leave'sδ¹³C values of the East and South of The Railway Station, Panxuan Road,Xizhan and Northwest Normal University are positive than the leave'sδ¹³C value of the North and West of it.This phenomenon is mainly caused by intensity. The leave'sδ¹³C values of the West and the North of the Refinery factory of Lan Zhou City and the Petrochemical Factory of Lan Zhou City are positive than the leave'sδ¹³C values of the East and the South of it.This phenomenon is mainly caused by pollution.2) There are differentδ¹³C values of Sophora japonica leaves between various sampling points of Lan Zhou City,the Northwest Normal University(-30.58‰)＜the Railway Station(-30.35‰)＜the Panxuan Road(-29.12‰)＜the petrochemical factory of Lan Zhou City(-28.54‰)＜the Refinery factory of Lan Zhou City(-26.45‰).And Xigu Region(-27.50‰)＞Lan Zhou City(-29.19‰)＞Chengguan Region(-29.73‰).The leavesδ¹³C values of the sampling areas are rising with the increasing concentration of sulfur dioxide and nitrogen dioxide,showing that the Ci values are decreasing and which is caused by the decreasing stomatal conductance.The leaves close the stomata to withstand the environmental pollution,embodying the resistance physiological characteristics of plant.3) Theδ¹³C values of photosynthetic organs of Sophora japonica are lower than the values of non-photosynthetic organs.Theδ¹³C values of leaves are 0.69‰～1.91‰, 2.31‰～3.20‰,2.93‰～3.65‰lower than the branches,thinks,barks.Theδ¹³C values of leaves are increased with the increasing concentration of atmospheric sulfur dioxide and nitrogen dioxide.Chemical composition is the main factor causing the different constitute of isotopic carbon in varied plant organs because the fractional distillation happened during the transport processes of photosynthetic can impact theδ¹³C values of trunks and barks.In that case,theδ¹³C values of branches,trunks and barks are more positive accordingly.