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Response Mechanism Of Masson Pine Seedlings To Drought Stress

Posted on:2019-08-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:W X QuanFull Text:PDF
GTID:1363330566473628Subject:Forest cultivation
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The Masson pine(Pinus massoniana Lamb.),is the most important native tree species in China because of its fast growing,high yield,high adaptability,comprehensive utilization and wide range of uses.It is widely distributed in the south of Qinling-Huaihe Mountains and east of the Yungui Plateau,17 provinces.Drought disasters seriously affect the growth and reproduction of Masson pine,its strong ability to absorb water from roots enhances adaptability to adverse conditions and makes Masson pine as one of the major pioneer tree species for afforestation.Improving the drought resistance of tree species is one of the main objectives of forest cultivation.Therefore,it is very important to study the adaptation mechanism of Masson pine to arid environment.In this study,Masson pine seedlings as the research object,the mechanism of Masson pine seedlings the response to drought was studied by the physiological and biochemical analysis,cytology,metabonomics,proteomics.This research provides science and technology support for afforestation and nursery of Masson pine in arid and semiarid regions.The main results are as follows:1.The physiological and biochemical changes of Masson pine seedlings under drought stress were preliminary clarified: 1)The soil water potential and needle water potential gradually decreased as the degree of drought deepened;drought stress affected the biomass allocation of Masson pine seedlings,and the seedling biomass,root/shoot ratio,seedling height,diameter,root length,and number of lateral roots were significantly lower than the control.Severe drought significantly inhibited the morphological growth of Masson pine,these indicators to some extent reflect the drought stress on the growth of Masson pine;2)The content of osmoregulation substances in Masson pine needles under drought stress was measured,the results showed that the content of soluble sugar,soluble protein,free proline and malondialdehyde gradually increased with the drought deepening.The increase of these substances relieved the drought stress to some extent.The antioxidant enzyme system could effectively scavenge active oxygen,ensure the normal physiological function of cells and maintain its resistance to drought stress.The CAT activity,SOD and POD enzyme activity of Masson pine needles showed an overall upward trend,which is conducive to scavenging free radicals and lowering,membrane lipid peroxidation level,thereby reducing the degree of membrane damage;The determination of endogenous hormones showed that the content of GA and IAA decreased with the deepening of drought stress,and the content of ZT and ABA increased gradually.The physiological parameters in the Masson pine needles are coordinated with each other to adapt the drought stress,and further study could be conducted.2.The relative contents of volatile organic compounds(VOCs)in different organs under drought stress were measured.The results showed that: 1)The main VOCs in the needles are ?-pinene,?-phellandrene,caryophyllene,etc.the trend of decreasing firstly and then increasing with the deepening of drought.The main VOCs in the stem segment were ?-pinene,?-elemene and caryophyllene,the change trend of the three substances in drought stress were different;?-pinene,d-longifolene,and caryophyllene are the main VOCs in the main root,and ?-pinene,?-elemene,3-carene were the main VOCs of the root tips;Cluster analysis showed that three VOCs,?-pinene,?-phellandrene and caryophyllene,played an important role in the drought resistance of Masson pine seedlings and were the main volatile components of Masson pine seedlings responding to drought stress.2)68 volatile materials were identified and analyzed by two-dimensional time-of-flight mass spectrometry,32 metabolites increased significantly and 4 metabolites decreased significantly under drought stress.3.The changes of photosynthetic characteristics of Masson pine seedlings under drought stress were clarified,The results showed that: 1)The net photosynthetic rate(Pn)and transpiration rate(Tr)of Masson pine decreased gradually with the deepening of drought stress,and the water use efficiency(WUE)increased first and then decreased.These indicators showed obvious threshold response to drought stress.Therefore,during the Pinus massoniana afforestation process,the threshold of soil moisture that seedling could maintain growth within the range of moderate drought,when the field capacity of water is 40%-75%,the Masson pine could gain the greater photosynthesis and water use efficiency.2)The decrease of Pn under mild and moderate stress was caused by stomatal limitation,and the decrease of Pn under severe drought stress was caused by non-stomatal limitation.RDA analysis showed that stomatal conductance(Gs)was the main driving factor for the photosynthetic characteristics(Pn,Tr,WUE)of Masson pine seedling,accounting for 94.30% of the explained amount of all environmental factors;NWC and softwood NWP It is the main influence factor of Gs,accounting for 94.00% of the total explanatory amount of all factors.The water content and water potential of Masson pine needles affect stomatal conductance,thereby affecting the photosynthetic rate of needles.4.The main results are as follows:(1)The cell structure of Masson pine roots,stems and needles under drought stress were destroyed,among them,cell rupture and collapse occurred under severe stress;2)The ultrastructure of Masson pine mainly consisted of chloroplast and mitochondria.Under the severe drought stress,the structure of chloroplast and mitochondria were severely damaged.The rupture of chloroplast matrix and basal granule was spread in the cell membrane,mitochondrial inner membrane structure was severely damaged and appeared large area of cavitation,the phenomenon of plasmolysis obvious and collapsed.5.Preliminary study of drought stress Masson pine seedling differential protein identification,screening and functional identification,and the results were following: through the analysis of protein expression,2533 drought-stress related proteins were found.There were 43 and 168 differential protein expressions under the CK: MD,and CK: SD,respectively.The functional analysis showed that the main metabolic pathways of differential proteins under drought stress were: biosynthesis pathway of secondary metabolites,endoplasmic reticulum,carbon metabolism,propane synthesis,glycolysis pathway,and starch and sucrose metabolism.These proteins may play an important role in drought resistance of Masson pine and adapt to the changes of arid environment through the expression of different protein functions.Conclusions: The work of this dissertation is based on proteomics methods combined with cell structure,physiological and biochemical indicators,and other indicators,preliminarily clarified the changes of the functional traits of Masson pine under drought stress.Through the above studies,it is clear that the volatiles and differential proteins in different organs of Masson pine under drought stress are of great significance for revealing the mechanism of drought resistance and drought tolerance of Masson pine.
Keywords/Search Tags:Pinus massoniana, drought stress, physiological and biochemical, volatile organic compounds, proteomics
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