The Characteristics Of Water And Chlorophyll Fluorescence Paramerters And Differential Proteomics Analysis Of Heteromorphic Leaves In Populus Euphratica Oliv.

Populus euphratica Oliv.is a pioneer tree and a natural protection shield for the desert forest ecosystem in northwestern China,praised as“hero tree of desert " due to characters tolerant to drought,sandstorms and salt.Thus,P.euphratica is considered an ideal plant to study the mechanism for survival of woody plants under adverse environmental conditions in deserts.On the other hand,P.euphratica is a distinct leaf shape ploymorphism from the lower to upper crown for the tree.The three typical heteromorphic leaves are lanceolate,broad ovate and dentate broad-ovate.The dentate broad ovate leaves showed more xerophytic form than others leaves,distributed in the upper crown where suffered more stress.In this dissertation,chlorophyll fluorescence combined with PV curve technique were used in the analysis of the leaf shape variation physiological mechanism of P.euphratica,and 2D-DIGE technique were established to separate the leaves proteins.The iTRAQ technology was applied to analyze the proteome expression in different leaf shapes of P.euphratica,and the detected proteins were analyzed by bioinformatic analysis,providing the theoretical basis for researches on drought/salt resistance mechanism for P.euphratica.The major results were as follows:1.Based on the tissue water relations parameters derived from PV curves,the water physiological characteristics of the leaves of P.euphratica were discussed.The dentate broad-ovate leaves had highest values of |ΨΠ100—ΨΠ0| and ε in the three typical shape leaves.The parameters would change with environmental conditions,such as ΨΠ100、ΨΠ0、|ΨΠ100—ΨΠ0| and ε.Compared to the parameters form trees grown in Beijing,these values of ΨΠ100 and ΨΠ0 of leaves from trees grown in WuHai decreased significantly,while |ΨΠ100-ΨΠ0| and ε had risen sharply.The dentate broad-ovate leaves could maintain leaf potential and turgor by descending the osmotic potential,widening osmotic adjustment ranges and thickening the cell wall.The water physiological characteristics of leaves made a corresponding adjustment with the change of water conditions,which reflected the water impact of leaf shape variation.2.The photosynthesis characteristics in the changes of leaf shape variation had been researched The results of chlorophyll fluorescence indicated that the values of qN were highest in lanceolate leaves,which showed that lanceolate leaves had lower energy efficiency.The respond of chlorophyll fluorescence parameters to drought/salt stress were also measured.Our results showed that at the earlier of drought/salt stress,all of the leaves exhibited resistance.With intensified drought/salt stress,differences of leaves stress tolerance became obvious.Under the drought/salt stress,the dentate broad-ovate leaves could keep in higher values of qN and qP than the other leaves,which indicated that the dentate broad-ovate leaves had better heat dissipation capability and could protect photosynthetic system from being damaged by the drought/salt stress3.Using iTRAQ technology,a total of of 2,689 proteins were quantified.Compared to lanceolate leaves,40 and 16 proteins significantly up-and down-regulated in broad-ovate leaves,respectively,and 40 and 33 proteins significantly up and down-regulated in dentate broad-ovate leaves.In addition,compared to the broad-ovate leaves,106 and 116 proteins significantly up-and down-regulated in the dentate broad-ovate leaves.Functional annotation results showed that these differentially expressed proteins had direct influences on physiological activities of leaves,such as photosynthesis,energy metabolism,cell wall formation,secondary metabolism,protein degradation and immune defense mechanisms.Lanceolate leaves had stronger light absorption capacity,weaker capacity to assimilate carbon and lower efficiency of photosynthetic products synthesis,which may resulted in light energy excess and weaker ability to cope with stress.When the trees were stimulated by the environment,the Ca2+ concentrations in leaf cells would change.The dentate broad-ovate and broad-ovate leaves had higher expression level of calmodulin,responding to outside stressors promptly.The expressions of SOD、APX and POD were enhanced to adjust the H2O2 accumulation in cell walls,influenced the process of phenolics oxidized to phenoxy and lignin polymerization reaction,and then adjusted the thickness of cell wall to defense stress.These changes were all consistent with physiological and biochemical functions as described above,which indicated that leaf variation of P.euphratica is a result from many complexity factors.4.This work established an available 2D-DIGE technique for proteomics research on leaves of P.euphratica.Differentially expressed proteins of lanceolate and dentate broad-ovate leaves were analyzed with the optimized 2D-DIGE technology,and]78 differential expressed protein spots were obtained.And a highly purified plasma membrane was isolated by using differential centrifugation combined with aqueous two-phase partitioning from the heteromorphic leaves.