Physiological Response Of Amygdalus Pedunculata Pall To Drought Stress

Amygdalus pedunculata Pall,Rosaceae,Amygdalus,Amygdalus,deciduous shrub,is a good tree species for soil and water conservation in arid and semi-arid areas and sandy edge areas of northwest China,is a plant with strong drought resistance,and has economic,ornamental,medicinal and other values.Because the drought is one of the main factors that lead to the plant unable to grow and develop normally,and this thesis studies the drought resistance of the physiological and biochemical indexes of Amygdalus pedunculata Pall to explore the response of Amygdalus pedunculata Pall to soil drought and the physiological limit of drought resistance,which can provide a reliable theoretical basis for Amygdalus pedunculata Pall cultivation and base construction.In this experiment,the drought stress test was carried out on Amygdalus pedunculata Pall by natural drought method,and the correlation and principal component analysis of photosynthetic gas exchange parameters,chlorophyll fluorescence characteristic parameters and physiological and biochemical indexes were carried out,and the drought tolerance threshold of Amygdalus pedunculata Pall was calculated,and the main conclusions of this thesis are as follows:(1)With the increase of drought stress,the plasma membrane permeability,malondialdehyde(MDA)and catalase content of Amygdalus pedunculata Pall showed an upward trend;The activities of superoxide dismutase(SOD)and peroxidase(POD),free proline(Pro),soluble sugar(Ss)and chlorophyll all increased first and then decreased with the intensification of drought stress.Soluble protein content and ascorbic acid(ASA)showed a direct downward trend.The results showed that Amygdalus pedunculata Pall had strong stress resistance to drought stress,and its stress resistance was mainly manifested by the increase of MDA,SOD and POD activities.(2)Under drought stress,the contents of chlorophyll a(Chla),chlorophyll b(Chlb)and total chlorophyll in the leaves of Amygdalus pedunculata Pall increased first and then decreased,but the response of Chlb to water stress was more sensitive than Chla,and the photosynthetic pigment content was the highest in the moderate stress(T2)stage.(3)With the strengthening of photosynthetically active radiation(PAR),the net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)generally showed an increasing trend,the intercellular carbon dioxide concentration(Ci)showed a downward trend,and with the intensification of drought,Pn,Gs and Tr all showed a downward trend,and Ci showed an increasing state.The light saturation point(LSP)and maximum net photosynthetic rate(Pnmax)of long-stemmed amygdala leaves were consistent under different moisture conditions,showing a trend of first rising and then decreasing,and decreased by 16.69% and 86.91% respectively at extreme coercion(T4)compared with CK.The light compensation point(LCP)showed an overall upward trend with the intensification of drought stress,and increased by 38.29% compared with 0 d treatment for 16 days.The dark respiration rate(Rd)showed a decreasing trend with the increase of drought days,and the value of Rd at CK was 2.17 times that of T4.(4)With the increase of drought stress,the initial fluorescence(Fo)increased significantly,the maximum fluorescence(Fm),the maximum photochemical quantum yield of PSII(Fv/Fm),and the effective photochemical quantum yield of PSII(Fv’/ Fm’)decreased significantly,photochemical quenching(q P)showed a downward trend,non-photochemical quenching(NPQ)showed an upward trend,in addition,the components of long-stemmed mandela lutein cycle system changed,the content of zeaxanthin(Z)and violaxanthin(V)increased,and the increase of zeaxanthin(Z)content at T4 was about 5 times that of violaxanthin(V)content.The results showed that drought stress reduced the part of the light energy absorbed by the pigment of the antenna in the PSII.reaction center of Amygdalus pedunculata Pall for chemical energy,and significantly increased the heat dissipation and fluorescence parts,and the primary reaction of photosynthesis was inhibited,resulting in a decrease in photosynthetic products,a decrease in photosynthetic rate,and the activation of the heat dissipation mechanism of plant lutein cycle system,thereby reducing the damage of drought to Amygdalus pedunculata Pall.(5)The correlation and principal component analysis of Amygdalus pedunculata Pall showed that Pn,Ci and Gs were used as principal components,and the cumulative contribution rate of the three was 98.34%,which was representative;According to the drought tolerance threshold analysis,the drought tolerance threshold of Amygdalus pedunculata Pall was about 12.4% in the severe stress(T3)-extreme coercion(T4)stage.