Establishment Of Steady-state Cholorophyll A Fluorescence Kinetics And Photosynthesis Of Overwintering Evergreen Broad-leaf Plant

The study consists of two parts.Firstly,theory of steady-state chlorophyllαfluorescnec kinetics was established.Secondly,through combining the theory and other means of photosynthetic research,utilization and distribution of solar energy of two kinds of evergreen broad-leaves plant were studied during overwintering in Beijing.The first part,in the case of actinic light adaption,if the light source was alternated by far red light,the photosynthetic electron transport chain of plant would be re-oxidated.In this case,re-illuminating actinic light,the O'-P'-F-C-S multisteps rise of fluorescence will be observed,which was named Steady-state Multistep(ie.SMS).Through treatment with chemical inhibition of the electron transport chain and adjustment of CO₂,the relation between SMS and the electron transporter and carbon assimilation was discovered.Every steps of SMS are controlled by Photosystemâ…¡(PSâ…¡),Cytb/f,Photosystemâ… (PSâ… ), FNR and carbon assimilation respectively.So the theory of SMS could detect the kinetics of PSâ…¡-PSâ… -carbon assimilation in light.Consequently,the theory was applied in many ticklish studies.Such as PSâ…¡-PSâ… -carbon assimilation of CAM plant,whose stomata were closed in light;the process of asymmetry closing of stomata in noon;regreening of golden leaves of golden privet and the PSâ…¡-PSâ… -carbon assimilation change in a series of stresses.All of these experiment prove that the new fluorescence approach opens the way for new insights into the complex interactions between PSâ…¡and PSâ… ,and the kinetic reactions after PSâ… in light adaption.The second part,by the means of SMS theory and OJIP theory,Photoinhibition and photoprotection modes of overwintering Euonmymus japonicus and Buxus spervirens L.in Beijing open gardens were investigated with instruments of PAM2100,Daul-PAM100, PEA and Oxylab,and OXYLAB.The acclimation mechanism of PSâ…¡-PSâ… -carbon assimilation kinetics of evergreen broad-leaves plant was discussed consequently.As onset of winter,both photochemical efficiency of PSâ…¡and photosynthetic rate decreased gradually,and the decrease of sun leaves were greater than that of shade leaves.In winter, kinetics of chlorophyll a fluorescence induction curves of sun leaves disappeared,which of shade leaves still existed.On the other hand,several mechanisms cooperated to effectively protect the photosynthetic apparatus from photodamage in winter.Firstly,decrease of minimal fluorescence(Fo)indicated that excitons of PSâ…¡were reduced through cutting the size of light-harvesting antenna.Secondly,the plant could maintain a steady photochemical quenching(qP),suggesting that excitons of PSâ…¡donor side were absorbed by keeping open of PSâ…¡.For the rate of carbon assimilation was slow,most electrons should be consumed by cycle electron transport chains or Mehler reaction.Besides,in winter,energy dissipation caused byâ–³pH or photosystem centers was the main way of heat dissipation, rather than light-harvesting antenna(NPQ).At last,for the different of species and domestication,the two kinds of plant have various capacity of resistment.High photochemical rate shade leaves of Buxus spervirens L.benefits from cooperation of linear electrons transport,non-lineary electrons transport and carbon assimilation.