Influence Of Crust-covered Paving On Physiological And Ecological Characteristics Of Firmiana Simplex

The pavement of crust-covered paving had changed the soil conditions,and resulted in the growth environment of plant deterioration,and thus brought about a lot of bad influence to green plants. Photosynthetsis and chlorophyll fluorescence analysis is an important means to study the mechanism of plant response to the environment. In order to explore the influence of crust-covered paving on the city landscape plants and provide a scientific basis for improving the growth environment and the health status of greening plants and reasonable planning of urban greening,the test measured the photosynthesis and chlorophyll fluorescence parameters,MDA content,SOD,POD,CAT activity,leaf moisture content and specific leaf weight etal.during may and july.The main results as follows:1.The diurnal variation of photosynthetic parameters showed that the croust-covered paving have brought a certain inhibiting to Firmiana simplex photosynthesis.Net photosynthetic rate (Pn) were overall slightly lower than the control,the difference was significant at 18:00;Transpiration rate (Tr) showed a single peak curve,while the control curve was bimodal,and were significantly higher than the control at 14:00,the differences as much as 45.08%.It changed basically with the change of light intensity and temperature;Water use efficiency (WUE) were overall slightly lower than that of control in addition to 16:00,the difference was not significant in the morning,but significant at in the afternoon;Stomatal conductance (Gs ) was significantly higher than the control at 14:00,lower than that of control at other times,but the difference was not significant;the intercellular CO2 concentration (Ci) were higher than the control in addition to 16:00,the difference was significant at 14:00 and 18:00.2.The changes of photosynthesis parameters in growing season showed that the influence of crust-covered paving on the Firmiana simplex more obvious in July under this experimental condition.The net photosynthetic rate (Pn) and transpiration rate (Tr) were overall slightly lower than the control throughout the growing season,the difference was significant in July;The water use efficiency (WUE) was higher than the control in may,slightly lower than the control in September and almost no difference from control in other months;The stomatal conductance (Gs) was slightly lower than the control between May and August and was slightly higher than the control between september and October,but the difference did not reach the significant level; Intercellular CO2 concentration (Ci) were also slightly lower than the control.3.The photo-inhibition of treatments were more serious than in the control at noon in July,but did not lead to the destruction of photosynthetic apparatus in leaves,the reaction center of PSâ…¡were short-lived and reversible inactivation,and showing a series of light protect adjustment mechanism.Under this experimental condition,the stress that crust-covered paving brought to Firmiana simplex can be restored,with the slack of light intensity and temperature.4.Under the crust-covered condition,the membrane permeability of Firmiana simplex leaves were increased,and the different parts of the leaves increase different range,the descending order is:the central of the leaf > the base the leaf > the apex the leaf;leaf moisture content and specific leaf weight were both reduced,and Separately reduce the rate of 6.41% and 15.3%;The Specific leaf area of treatment was 18.06% higher than that of the control,but the difference did not reach the significant level.