Photosynthetic Physiology Response Of Five Landscape Trees Exposed In Different Environments

Urban road afforesting trees is not only beautiful to serve its function,but also to improve the city's ecological environment.At the same time,traffic pollution as the city's main sources of pollution will also restrain the growth of tree species.Photosynthesis is the basis of plant metabolism,and very sensitive to changes in the environment,small changes in environmental conditions or environmental substances would give rise to micro-changes and first appeare in the plants photosynfhetic indicators of change.Therefore,this paper deals with the study of five gardens in Harbin,Salix alba var Tristis,Prunus maackii,Syringa oblata,Cornus stolonifera,Ulmus pumila as the research object,in traffic pollution and a relatively clean area,giving an dynamic observation of the net photosynthetic rate,stomatal conductance, intercellular CO₂ concentration,transpiration rate,light response curves,and an analysis of five species of traffic pollution on photosynthesis in response to physiological differences, providing basis for rational choice for road afforesting trees.The research shows that,(1)To relatively clean area,traffic pollution net photosynthetic rate,stomatal conductance,intercellular CO₂ concentration,transpiration rate of five kinds of tree species.In every month there are different degrees of decline,decrease of plant species due to the month and vary.This shows that affected by traffic pollution stress,photosynthetic capacity of five tree species is subject to suppression.(2)Under the environment in traffic pollution,to the relatively clean area,net photosynthetic rate of five kinds of tree species is lower,The monthly averages of five garden trees reduce to 17.79%,29.84%,38.65%,31.87%and 36.13%respectively.and the highest Absenkungswert m in August which also has the most significant differences.The descender of net photosynthetic rate of Populus alba×P.berolinensis is smaller monthly.(3)Similar to net photosynthetic rate,stomatal conductance,transpiration rate showed a downward trend,the law of decline is basically the same as its changes in net photosynthetic rateIt explains the high relativity between them.In August transpiration rate of five kinds of trees species all have a higher drop.Populus alba×P.berolinensis reduced 35.79%,Syringa oblata reduced 46.59%,Prunus maackii redued 53.5%,Cornus stolonifera reduced 70.49%,Ulmus pumila reduced 62.2%.Between July and October,the transpiration rate of Populus alba×P.berolinensis have a smaller decrease in five tree species,this shows that transpiration rate of Populus alba×P.berolinensis is affacted a low degree by the traffic pollution.(4)The environment pollution of traffic to the intercellular CO₂ concentration of five species did not significantly affect.From September,the intercellular of CO₂ in five tree species in the transport contaminated area is higher than the relatively clean zones gradually,the differnces of Prunus maackii is the largest,increase 16.17%and this shows that the intercellular of CO₂ in Prunus maackii is affacted by Environmental stress by the traffic pollution is large,and low resistance.(5)The maximum net photosynthetic rate(Pmax),the apparent quantum efficiency (AQY),dark respiration rate(Rd)and light compensation point(LSP)of five species in zoon of traffic pollution have a downtrend comparing to relatively clean area,but the light saturation point LCP shows an uptrend.