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低温胁迫恢复过程中不同回温速度对油茶光系统活性的影响
Effect of temperature return rate on photosystem activity of Camellia oleifera during recovery from low temperature stress
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摘要: 为探讨低温胁迫及不同回温速度对油茶光系统I(PSI)和光系统II(PSII)活性的影响,以2年生‘长林40’油茶嫁接苗为试验材料,低温(−5 ℃)胁迫24 h后,以30、5、2.5 ℃/h速度升温至室温(25 ℃),测定油茶叶片叶绿素荧光快速诱导动力学曲线和对P700+氧化还原动力学曲线,并进行叶绿素荧光淬灭分析。结果表明:低温胁迫24 h后,油茶叶片PSⅡ和PSⅠ的活性均发生不同程度的光抑制。在恢复阶段,PSII和PSI活性对回温速度均比较敏感,PSII活性随着回温速度的增加而加快;与此同时,PSI活性在快速回温速度(30 ℃/h)下恢复较慢,在慢速回温速度(2.5 ℃/h)下恢复较快。快速回温促进了油茶叶片线性电子传递速率的恢复。温度回升越快恢复过程中的PSⅡ向PSⅠ传递的电子数量更多。而过多电子数量降低了P700氧化水平,进一步加剧了PSⅠ的光抑制。因此,在油茶低温胁迫恢复过程中,较快的回温速度下PSII活性恢复的加快会引起流向PSI的光合电子的增加,进而加剧PSII和PSI活性的不匹配,生产中应当在低温发生之后采取措施防止温度回升过快,从而有利于油茶光系统的保护和修复。Abstract: Low-temperature stress is a common adverse condition in oil tea cultivation during winter and spring, which greatly impacts plant photosynthesis. The investigation found a close correlation between low temperature injury and the temperature return rate after low temperature relief. The sharp rise in temperature after low-temperature is often accompanied by serious low temperature injury. In this study, the effects of low-temperature stress and different temperature return rates on the activity of photosystem I (PSI) and photosystem II (PSII) of Camellia oleifera were investigated. 2-year-old potted seedlings of Camellia oleifera 'Changlin40' were used as the test material. After being stressed at low temperature (−5 ℃) for 24 hours, the temperature was heated to room temperature(25 ℃) at rates of 30, 5, 2.5 ℃/h. The rapid induction kinetic curves of chlorophyll fluorescence and the redox kinetic curves of P700+ were determined, and the chlorophyll fluorescence was quenched. After 24 hours of low-temperature stress, photoinhibition of PSⅡ and PSⅠ activities of Camellia oleifera leaves occurred to different degrees. In the recovery stage, both PSII and PSI activities are sensitive to the return temperature rate, and PSII activity accelerates with the increase in the return temperature rate. At the same time, PSI activity recovers slowly at the fast return temperature rate(30 ℃/h) and faster at the slow return temperature rate(2.5 ℃/h). Rapid temperature rise promotes the recovery of linear electron transfer rate in Camellia oleifera leaves. The faster the temperature rises, the more electrons are transferred from PSⅡ to PSⅠ during the recovery process. The excessive number of electrons decreases the oxidation level of P700, which further intensifies the photoinhibition of Pⅰ. In the recovery process of Camellia oleifera under low-temperature stress, the acceleration of PSII activity recovery at a faster temperature return rate will lead to an increase in photosynthetic electrons flowing to PSI, further aggravating the mismatch between PSII and PSI activities. Measures should be taken to prevent the temperature from rising too fast after the occurrence of low temperature in production, to facilitate the protection and repair of Camellia oleifera photosystem.