The Influence Of Ozone And Light Stress On Physiological Function Of Grape Leaf

As the climate warms,the concentration of ozone in the atmosphere continues to rise.The photooxidation of ozone under the strong light synergy causes serious damage to sensitive crops such as grapes,resulting in photoinhibition of grape leaf photosynthesis and even irreversible damage of photosynthetic apparatus,but the mechanism of influence of high concentration of O₃ and light stress on grape leaf physiology and structure are still not very clear.In this paper,Cabernet Sauvignon was used as a test material to study the response of photosystem I and photosystem II activity and the change of leaf tissue anatomy under the cooperative stress of O₃ and light.At the same time,Moldovan and White grapes were used as materials to study the alleviation effect of exogenous ascorbic acid and long-term shading on O₃ stress.The main results were as follows:1.In the dark state,MDA content increased significantly,NPQ significantly increased,andΦ_PSII decreased significantly in O₃ stress treatment（T1）compared with control CK,but there was no significant change in stomatal opening and chloroplast ultrastructure;under light-conditioned conditions,O₃ stress Treatment（T2）significantly decreased stomatal opening compared with control CK,guard cell K⁺efflux,chloroplast number,chloroplast basal granule number and basal lamella number of mesophyll cells decreased significantly,chlorophyll content significantly decreased,and MDA content increased significantly by 39.4%,F_v/F_m decreased significantly by 15.2%;Under strong light conditions,chlorophyll content further decreased significantly with chlorophyll content,chlorophyll content,chlorophyll content,chlorophyll content,chlorophyll content,chlorophyll content,chloroplast content,chloroplast content,chloroplast content,chloroplast content,and chlorophyll content.Further increase,guard cell K out-row but the degree of stomatal opening further reduced,while the leaves F_v/F_m andΦ_PSII to a minimum.2.O₃ stress resulted in a significant decrease in photosynthetic performance of grape leaves.Compared with the control,F_m decreased significantly by 17.0%;F_v/F_m value decreased by11.1%.At the same time,RC/CS_o decreased by 44.1%.Y（I）and Y（II）decreased significantly by 33.0%and 50.1%,respectively,and only the P_m value did not change significantly.After the introduction of Lincomycin Lin,the F_m and F_v/F_m decreased significantly by 23.3%and19.7%compared with the O₃ stress alone treatment,but P_m decreased but there was no significant difference and Y（II）decreased significantly.In 26.0%,Y（NPQ）decreased significantly by 23.1%and Y（NO）increased by 35.4%,but Y（I）,Y（ND）,and Y（NA）parameters that reflect PSI performance did not change significantly.In the recovery process after O₃ stress,with the increase of recovery time,the leaf conductance of T3 treatment（O₃+light）increased significantly,but the conductivity of T1 and T2 treatment leaves did not increase significantly.The values of Y（I）in dark ozone and photooxidation ozone increased to a certain extent compared with the control.The Y（I）value of intense light ozone treatment decreased continuously,and the Y（I）value was close to 0 at 13 hours.Ozone-dark and ozone-adaptive light treatment Y（II）values increased to a certain extent,while ozone-light treatment Y（II）values remained at a low level.3.The F_m of grape leaves treated with long-term O₃ gradually decreased,while the F_m of CK grape leaves remained at about 3.2.The Fm values of grape leaves after 4 weeks,8 weeks and12 weeks of O₃ treatment were respectively decreased by 12.4%,23.3%and 55.5%compared with the control.The SPAD values decreased by 4.4%,6.3%and 9.5%respectively compared with the control.Soluble sugars in fruits were also significantly decreased by 33.1%compared with CK.Total tannin content and total phenol content were significantly decreased by 48.1%and 17.6%,respectively,compared with CK.4.Long-term shading alleviated the decrease of the maximum photochemical efficiency Fv/Fm,the actual photochemical efficiency of lightΦ_PSII and the photochemical quenching coefficient qP,and at the same time alleviated the increase of non-photochemical quenching.Long-term shading reduced the soluble solids of grapes.However,the effect was not significant.5.During the growing season,the field’White’grape leaves showed obvious O₃ damage symptoms.After exogenous ascorbic acid spraying,the leaf chlorophyll content,P_n and F_v/F_m of the’White’grape increased by 30.02%and 59.84,respectively.The chlorophyll content and net photosynthetic rate increased by 23.67%and 69.74%after urea spraying,respectively,compared with the control.The results showed that the exogenous ascorbic acid and urea spraying alleviated the inhibition of ozone stress on the photosynthetic electron transport chain of grape leaves,improved the distribution and utilization of light energy,and mitigated the effect of O₃ stress on grape leaves.The effect of ascorbic acid was obvious.