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Study on Antioxidant Properties of Heteromorphic Leaves of Populus Euphratica Oliv.CN

李萍萍

北京林业大学

Abstract:Populus euphratica Oliv.,commonly known as a desert poplar,is a pioneer trees pecies with the charaters of stress resistance and heteromorphic leaves in western China.Previous studies have demonstrated that the structural characteristics of P.euphratica from lanceolate leaves to dentate broad-ovate leaves are related to its eco-adaptability.In the present study,to elucidate the regulation mechanisms of stress tolerance,we focused on the antioxidant capacity of three heteromorphic leaves of P.euphratica.Here the chlorophyll content,the stability of cell membrane,osmotic regulator substance contents and antioxidant system indeices in lanceolate leaves,ovate leaves and dentate broad-ovate leaves,three typical morphological leaves of adult P.euphratica,were studied in different seasons.The results were as follows:1.There were differences in chlorophyll content and chlorophyll a/b among the three morphological leaves.With the change seasons,the content of chlorophyll increased in lanceolate leaves,firstly increased and then decreased in ovate leaves,while it decreased in dentate broad-ovate leaves.The content of chlorophyll a was higher than chlorophyll b in three morphological leaves.And the chlorophyll a/b value in dentate broad-ovate leaves was the highest,follewd by ovate leaves,was the lowest in lanceolate leaves.The chlorophyll contents in ovate leaves and dentate broad-ovate leaves were significantly higher than that of lanceolate leaves in May and July.Although the chlorophyll content in dentate broad-ovate leaves decreased in September,but it increased the utilization of light energy by increasing the chlorophyll a/b value,which was an adaptation to the strong light in summer and shortened light time in autumn in the upper part of the canopy.2.There were differences in the osmotic regulation ability among three types of leaves.With the change of seasons,the contents of proline and soluble protein in heteromorphic leaves of P.euphratica were increased,and the content of soluble sugar decreased in lanceolate leaves,while it decreased firstly and then increased in both ovate leaves and dentate broad-ovate leaves.In general,From lanceolate leaves to dentate broad-ovate leaves,there was an obvious increase in the content of osmotic adjustment substances,indicating that dentate broad-ovate leaves had the strongest osmotic adjustment ability and had strong adaptability to strong light and water deficit stress.3.There were differences in ROS metabolism among three morphological leaves.The rate of the O2·-production firstly increased and then decreased in lanceolate leaves,while it progressively increased both in ovate leaves and dentate broad-ovate leaves.The content of MDA increased in lanceolate leaves,firstly decreased and then increased in ovate leaves,while it decreased in dentate broad-ovate leaves all the time.The relative conductivity values of three morphological leaves changed slightly and the difference was not significant.And Scavenging rate of DPPH firstly decreased and then increased in lanceolate leaves and ovate leaves,while it decreased in dentate broad-ovate leaves.It is noteworthy that compared to the other types of leaves,O2·-production rate was the lowest while MDA content was the highest in lanceolate leaves in September.The results showed that the cell membrane stability of the three morphological leaves was better,but the levels of reactive oxygen species were significantly different.4.There were differences in the indeices of antioxidant system in three morphological leaves.With the change of seasons,the activities of SOD,POD,CAT,APX and GR in lanceolate leaves all firstly increased and then decreased.Both in ovate leaves and dentate broad-ovate leaves,the activity of SOD firstly decreased and then increased,while the activity of CAT firstly increased and then decreased.There was a progressively increase of the activity of POD,and a decrease of activity of GR.The activity of APX firstly increased and then decreased in dentate broad-ovate,and it progressively increased in ovate leaves.Overall,the activities of antioxidant enzymes in dentate broad-ovate leaves>ovate leaves>lanceolate leaves.Furthermore,the difference of POD activity was the most obvious among the three types leaves.POD isozyme electrophoresis showed that three morphological leaves had the same number of POD isozyme bands,and the activity of POD in dentate broad-ovate leaves was the highest,while that of lanceolate leaves was the lowest.And the contents of flavone and carotenoid firstly increased and then decreased both in dentate broad-ovate leaves and ovate leaves,while them were increased in lanceolate leaves.The content of AsA progressively increased both in dentate broad-ovate leaves and ovate leaves,while it firstly decteased and then increased in lanceolate leaves.In addition,the content of GSH all decreased in three morphological leaves.In three morphological leaves,a large amount of flavones and carotenoids were synthesized in July,and a large amount of AsA was generated in September.The results showed that the accumulation of ROS not only enhanced the activities of antioxidant enzymes,but also promoted the accumulation of antioxidant substances.Correlation analysis:the activities of antioxidant enzymes(POD,CAT and APX)and the contents of flavone and carotenoid were all highly significantly and positively correlated with the O2·-production rate in lanceolate leaves(P<0.01),and in addition to POD,APX and carotenoid,the O2·-production rate was significantly and positively correlated with AsA content in ovate leaves(P<0.01).And there was a significantly and positively correlated between the O2·-production rate and APX activity,carotenoid content in dentate broad-ovate leaves(P<0.01).These results showed that the mechanisms of scavenging reactive oxygen species were different among three morphological leaves.With the seasonal changes,dentate broad-ovate leaves in the upper part of the crown and ovate leaves in the middle part of the crown were stressed by strong light and water shortage,so they had stronger antioxidant capacity,while lanceolate leaves in the lower part of the crown had weaker antioxidant capacity.
  • Series:

    (D) Agriculture

  • Subject:

    Forestry

  • DOI:

    10.26949/d.cnki.gblyu.2019.000928

  • Classification Code:

    S792.11

Tutor:

郑彩霞;

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