The Study On Relationship Between The Excitation Of Ultraweak Luminescence And The Chloroplast And Its Function In Cerasus Humilis Leaves

At present,the study of ultraweak luminescence（UWL）in plants has just started,and the source and mechanism of its production are far from clear.In this research,the changes of chloroplast functions（including chlorophyll metabolism,photosystem activity,photosynthetic performance,chloroplast structure etc.）and the changes of UWL were studied in leaves of Cerasus humilis under the regulation of salt stress and light stress.The research aimed to investigate the relationship between UWL and chloroplast,chlorophyll metabolism,photosystem activity,finally found out the mechanism of origin of UWL from chloroplast focusing on the chlorophyll metabolism and photosystem activity.The research aimed to provide a theoretical basis for revealing the relationship between UWL and plant growth physiology and the source of UWL production in plants.The main results of this study were as follows:1.Under salt stress and light stress,the UWL intensity of Cerasus humilis leaves decreased with the extension of the stress time,and the more severe the stress degree,the faster the UWL intensity decreased.2.Under salt stress and light stress,the changes of Chl metabolism and Chl content in Cerasus humilis leaves were different.Salt stress reduced the content of Chl synthesis precursors and Chl content;UWL decreased accordingly;correlation analysis showed that UWL was significantly positively correlated with Chl synthesis precursors and Chl content under salt stress.Light stress promoted the Chl metabolic process,increased the chlorophyll synthesis precursor and metabolic enzyme content,thereby increasing the Chl content;at the same time,the UWL intensity decreased;further correlation analysis results showed that the light stress Chl synthesis precursor,metabolic enzymes and Chl were negatively correlated with UWL.Under salt stress and light stress,the photosynthetic activity of Cerasus humilis leaves was severely inhibited,the oxygen evolving complex（OEC）activity reduced,the integrity of thylakoid membrane reduced,and the photochemical efficiency of photosystemⅡ（PSⅡ）reduced,the overall performance index declined,Q_A-Q_Belectron transfer blocked,and the photosystemⅠ（PSⅠ）reaction center over-reduced,which led to the hindrance of energy synthesis and the decrease of energy level,photosystem activity decreased.At the same time,UWL intensity decreased under both stresses.Further analysis of the correlation between the indicators of photosystem activity and UWL showed that UWL was significantly related to the main parameters F_V/F_m,F_V/F_O,PI_ABS,RC/CSm,φ_E0,Ψ_E0and the absorption and capture of energy on the unit reaction center or unit leaf section,transmission,utilization and dissipation.The experiment showed that the photosystem activity of Cerasus humilis leaves was related to the production of UWL.The intensity of photosystem activity affected the intensity of UWL,and the intensity of UWL decreased with the decrease of photosystem activity.Under salt stress and light stress,the net photosynthetic rate（Pn）,transpiration rate（Tr）,and stomatal conductance（Gs）of Cerasus humilis leaves decreased,while the intercellular CO₂concentration（Ci）increased,which showed that the photosynthetic performance of Cerasus humilis leaves decreased;UWL intensity decreased accordingly.At the same time,correlation analysis showed that UWL was significantly positively correlated with Pn,Tr,Gs,and significantly negatively correlated with Ci.It showed that the photosynthesis of Cerasus humilis leaves was related to the production of UWL.The intensity of UWL and photosynthetic performance affected the intensity of UWL.UWL intensity decreased with the decline of photosynthetic performance..3.Under salt stress and light stress,the ultrastructure of chloroplasts of Cerasus humilis leaves was destroyed,the greater the degree of stress,the more serious the structural damaged.The main manifestations were loose internal structure,degradation of thylakoids,fuzzy basal granules,and disappearance of starch granules.The destruction of chloroplast structure directly led to the reduction of chloroplast function.4.Based on the above results,Chl metabolism and Chl content were affected when the Cerasus humilis leaves were under salt stress and light stress.Photosystem activity decreased,energy production efficiency and energy level decreased,resulting in the decrease of photosynthetic performance.The above results indicated that photosynthesis decreased.At the same time,the chloroplast structure was destroyed under the two stress conditions.Both the decline of chloroplast photosynthesis and structural damage indicated the decline of chloroplast function under stress,decreased chloroplast function eventually affected UWL excitation and the decrease of UWL intensity.The above results revealed that chloroplast function was closely related to UWL,and chloroplasts were one of the organelles that stimulate UWL.