Physiological And Biochemical Characteristics Of Old Tree Aging Condition

Old trees are bear witness of a long history of countries and cities,is an important component of the natural and cultural heritage.Beijing which is the capital of five dynasties,has a history of 3000 years,and is rich in old tree resources.However,with changes in the urban environment and frequent human activity,the survival and the protection of old trees faced with many problems,many old trees weakened or even death every year.so,study the causes of weakening and death of old trees,and implement targeted rejuvenation and protection will benefits future generations.Chloroplast ultrastructure of Chinese pine and oriental arborvitae of different age and growth state were observed and analysised,and chloroplast membrane structure and the containing materials were studied in this experiment;and we also measured photosynthetic characteristics on the ground.Secondly,the photosynthetic characteristics of the trees were further explored from different perspectives by using chlorophyll fluorescence kinetics.In addition,we focus on the relationship between plant hormones and weaking of old trees.Finally,rbcL gene was cloned and analysised to explore the difference of the photosynthesis ability of old trees with different levels,in order to study the strength of their growth activity.Chloroplast Ultrastructure observation showed that there is a significant difference between strong and weak tree,age of the strong trees do not affect the chloroplast ultrastructure,but the difference between different age weak trees is obvious.Through the modulation of chlorophyll fluorescence detected that,Yield value,ETR and qP value significantly reduced with the weakness increase of the trees,but qN values on the contrast.This shows that weak tree decline in photosynthetic capacity.Study of membrane lipid peroxidation found that,MDA content increased significantly with weak deepening and age growth of trees.Study of endogenous hormones showed that IAA content decreased,ABA content increased gradually with the degree of understanding aging,the relationship between the two hormones was the growth and decline.RbcL gene sequence comparison showed that the probability of rbcL gene mutation got larger with age increasing,in that the differences by encoding Rubiso large subunit arised,which impact the capacity of photosynthesis and photorespiration of old trees greater.