Research About Water Use Efficiency Of The Typical Tree In Bejing Under Different CO2 Concentration

The changes of CO2 concentration caused by climate change is becoming more and more attention,because of the civil population distribution and uneven development in China,show the north environmental CO2 concentration is higher.So,it can proviede basis for a more comprehensive build vegetation environment and respond to CO2 concentration changes,that study the physiological and ecological effect of north typical plant under CO2 concentration changes.Experiment selected broad-leaf species of Platycladus orientalist and coniferous species of Quercus variabilis in Beijing mountainous area.Through the indoor experiment of incubator control environment factors,and use the photosynthetic apparatus,electron microscope and isotope method,study that stomatal behavior,photosynthetic parameters and instantaneous water use efficiency,physiological and ecological factors influence each other under 400 μmol/mol,500 μmol/mol,600 μmol/mol,800 μmol/mol.Research conclusions are as follows:(1)Stomata is main channels that gas exchange of plant leaves with the outside world,it is through their own adjustment to control involved in CO2,O2,and water vapor of photosynthesis and transpiration. Study said that transpiration rate and stomatal conductance show negative correlation with the environment CO2 concentration of Platycladus orientalist.When CO2 concentration on 400 μmol/mol to 800 μmol/mol and soil moisture under the condition of severe drought or field capacity,the most stomatal number is on 400 μmol/mol what the stomata density range of Platycladus orientalist is 160 individual/mm2.A minimum of stomatal number is on 800 μmol/mol,what is 123 individual/mm2.Preliminary know that the stomata density range of Platycladus orientalist is 110～170 individual/mm2.A single leaf stomatal density is different in different positions in four concentration gradient,from the tip of the blade to the bottom stomatal density is bigger and bigger,the leaf apex is 50-140 individual/mm2,leaf middle is 100-170 individual/mm2,leaf bottom is 130-190 individual/mm2,that leaf apex<leaf middle<leaf bottom.Under the same soil moisture conditions stomatal opening ratio with the increase of CO2 concentration decreases.Low concentration of 400 μmol/mol is 26%-50%,high concertration of 800 μmol/mol is 16%-41%.(2)The result is net photosynthetic rate(Pn) and intercellular CO2 concentration(Ci) show positive correlation with the environment CO2 concentration,transpiration rate(Tr) and stomatal conductance(Gs) present negative correlation with the CO2 concentration.When the soil moisture of severe drought,the photosynthetic parameters according to the environmental CO2 concentration rising from 400 to 800 μmol/mol by per 100 μmol/mol of Platycladus orientalist and Quercus variabilis,range of Pn is 15～34%、3～44%,range of Tr is 2-49%、18～24%,range of Gs is 10～17%、20～50%,range of Ci is 2～22%、12～42%;When field capacity, Platycladus orientalist and Quercus variabilis that range of Pn is 8～62%、0.8～62%,range of Tr is 5～9%、16～37%,range of Gs is 8～23%、10～60%,range of Ci is 1～36%, 14～26%.The results show through significant ana\ysis,Platycladus orientalist under different CO2 concentration treatment of Ci were very significant differences,Quercus variabilis under different CO2 concentration processing Tr and Gs and Ci are very significant differences.(3)Instantaneous water use efficiency in plants can reflect the status of plant growth and adaptability to the environment.Under the severe drought,instantaneous water use efficiency (WUEi) of Platycladus orientalist and Quercus variabilis increases with the increase of CO2 concentration,the growth ratio range of 15%～40% and 6%～60% respectively. Under the field capacity processing,the WUEi along with the increase of CO2 concentration increased after decreased first, fluctuation range of 0.4%～55% and 2%～55% respectively;Under the same water treatment and CO2 concentration,Quercus variabilis than Platycladus orientalist about WUEi,and Quercus variabilis WUEi range fluctuation is bigger also. WUEi of Platycladus orientalist and Quercus variabilis in severe drought with environment were very significant,CO2 concentration under the condition of field capacity WUEi and environment relationship was not significant.Need special pointed out that under the water reach the field capacity of Quercus variabilis WUEi along with the increase of CO2 concentration and no obvious change trend,to research the reasons.(4)Leaf stomata open rate and stomatal conductance of Platycladus orientalist were reduce with the environment by the rise of CO2 concentration.Stomata opening ratio and stomatal conductance presented positive correlation,both under the condition of the CO2 concentration processing,the soil moisture of severe drought correlation were 0.79914,0.82460,0.86277,0.79914,when the field capacity were 0.37214,0.57899,0.54865,0.57899,and the correlation with the increase of CO2 concentration environment also rise.In the concentration of 800 μmol/mol,severe drought and field capacity of slope is the biggest change,under high concentration stomata behaviors effects more volatility,more complicated.(5)Increased environmental CO2 concentration from low concentration to high concentration,Gs of Platycladus orientalist is reduced under drought conditions while WUEi increases,both with the CO2 concentration gradient in opposite change tendency;And field capacity under the condition of water using Gs gradually with the increase of CO2 concentration is reduced,and WUEi did not showed regular changes.