Effects of Low-Temperature Stress on Chlorophyll Fluorescence Parameters and Antioxidant System of Bougainvillea in the Context of Climate Change
[Objective]This study is aimed to explore the physiological and biochemical manifestations of Bougainvillea spectabilis Willd.to low temperature and the intrinsic adaptation mechanism to cold stress in the context of climate change.[Methods]Taking Bougainvillea Paederia Foetida,Bougainvillea Flaming Sumba and Bougainvillea Duranta with strong,medium,and weak cold tolerance as test materials,through indoor pot experiments,we conducted low temperature treatments for 7,14 and 21 days and studied the responses of the photosynthetic and antioxidant systems of different cold tolerant Bougainvillea to cold stress during these different periods.[Results](1)During the low-temperature treatment period,the initial fluorescence(F0)of all varieties increased,with the most significant change in B.Paederia Foetida,which increased by 60.2％compared to day 0.Maximum fluorescence(Fm),PSII effective photochemical electron production(Fv/Fm),and photosynthetic relative electron transfer rate(ETR)rapidly decreased and reached their lowest levels at day 21.As the intensification of low temperature stress,the photochemical quenching coefficient(qP)of the three Bougainvillea types decreased,while the non-photochemical quenching coefficient(qN)of B.Flaming Sumba and B.Paederia Foetida increased significantly.(2)After exposure to low temperature stress,the activities of SOD,POD and CAT enzymes in each variety decreased significantly and intensified with the extension of stress time,indicating that low temperature seriously inhibited the antioxidant enzyme activity of Bougainvillea.Among them,the SOD,POD and CAT enzyme activities of B.Paederia Foetida were higher than those of the other two varieties,indicating that B.Paederia Foetida had strong cold resistance.(3)In the AsA-GSH cycle system,the content of AsA and DHA of each Bougainvillea leaf significantly increased under low temperature.Compared to day 0,the GR activity of the three Bougainvillea types at day 21 increased by 180.91％,175.97％and 112.37％,respectively.Additionally,the AsA/DHA ratio,APX activity and DHAR activity of B.Paederia Foetida significantly increased at day 21.[Conclusion]Low temperature inhibited plant growth through affecting the PSII photochemical reaction center.However,Bougainvillea could activate their photosynthetic system protection mechanism to reduce photoinhibition.Furthermore,it could accumulate osmoregulation substances,activate the antioxidant system,and exert stress regulatory effects to eliminate rapidly proliferating ROS in its own body and alleviate low-temperature damage.
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