Antioxidant response mechanism of Tainong No.1 mango under simulation enhanced UV-B radiation
[Objective]The purpose of the study was to investigate the response mechanism of antioxidant reduction components of Tainong No.1 mango pulp under strong UV-B radiation,so as to provide a theoretical reference for mango production under global climate change.[Method]Natural light irradiation was used as the control,and the artificial simu-lation enhanced UV-B radiation with an intensity of 96 kJ/(m2·d)was set up.In 2021,mango pulp samples were taken every 10 d from 30 d after anthesis(December 18)to 90 d after anthesis(February 17,2022)and from 40 d after anthe-sis(December 1)in 2022 to 90 d after anthesis(January 21,2023),for a total of 7 and 6 samples,respectively.The con-tents of total flavonoids,total phenols,superoxide anion hydrogen peroxide(H2O2)and malondialdehyde(MDA),as well as the dynamic changes of phenylalanine ammonia-lyase(PAL)and polyphenol oxidase(PPO)enzyme activities and relative electrical conductivity(REC)were measured in the pulp at each sampling period.[Result]After enhanced UV-B radiation treatment,the content of superoxide anion in reactive oxygen species(ROS)of the first year and the se-cond year increased gradually with the increase of time,and superoxide anion at 90 d after the first year and 70 to 90 d after the next year was significantly higher than that of control(P<0.05,the same below).The variation trend of H2O2 under radiation treatment was firstly decreased and then increased in the first year,and only the radiation treatment at 90 d after anthesis was significantly higher than the control,H2O2 in the next year decreased,and the radiation treatment at 70 to 90 d after anthesis was significantly higher than the control.The contents of total phenol and total flavone in mango pulp showed a decreasing trend at 2 years.The contents of total phenol at 50 d after anthesis in the first year and 50 and 60 d after anthesis in the next year were significantly higher than those of control under radiation treatment.The 2-year change trend of MDA content and REC was decreased and then increased.MDA content in the first year was significantly higher than that in the control group at 40 d after anthesis and 50 d after anthesis in the next year,while MDA content and REC were significantly higher than that in the control group at 90 d after anthesis.The PAL activity of mango pulp treated with radiation showed a trend of decreasing,increasing and decreasing at the first year.The PAL activity of mango pulp treated with radiation was significantly higher than that of control at 40 d after anthesis,and there was no significant dif-ference at 90 d after anthesis.In the next year,there was an upward-downward-upward trend,and there were significant differences between 50-70 d after radiation treatment.The dynamic changes of PPO activity at 2 years showed a trend of first decreasing and then increasing.In the first year,the activity of PPO at 40,60,70 and 80 d was significantly higher than that of the control,and in the next year,the activity of PPO at 60 and 90 d after anthesis was significantly higher than that of the control.[Conclusion]Mango treated with enhanced UV-B radiation mainly control the synthesis of pheno-lic compounds dominated dominated by flavonoids through regulating PAL activity and act as efficient antioxidants against UV-B radiation.
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