低温胁迫及恢复对番茄快速叶绿素荧光诱导动力学特征的影响

以番茄品种“中蔬4号”为试材，设置对照（人工气候室，温度变化范围18～28℃，600μmol?m?2?s?1，光周期12h，CK）和低温（人工气候箱，8℃，200μmol?m?2?s?1，光周期12h，CL）两个处理，低温处理4d后将番茄幼苗移入对照环境下恢复4d，观测叶片快速叶绿素荧光诱导动力学曲线在低温处理及恢复期的变化，以探讨低温胁迫和随后恢复对番茄叶片光系统II（PSII）反应中心和受体侧的影响。结果表明：低温胁迫降低了番茄叶片PSII光化学效率和光合性能，导致低温光抑制的发生。低温胁迫导致番茄叶片单位面积有活性的反应中心数目（RC/CS）及其开放程度（Ψo）下降，从而降低了叶片单位面积对光能的吸收（ABS/CS）、捕获（TRo/CS）和进行电子传递（ETo/CS）能力，减少了电子传递到电子传递链中超过QA?电子受体的概率（φEo），阻碍了光合电子传递的进行；与此同时，低温首先诱导了PSII可逆失活和热耗散增强以减少对过剩光能的吸收、传递与积累，随后促进了PSII受体侧电子传递体PQ库容量（Sm）增大以防御PSII过量激发压积累。本实验中低温主要抑制了番茄叶片PSII活性，而对PSI影响相对较小。恢复期天线色素对光能的吸收和PSII反应中心对光能的捕获能力较电子传递更易于恢复，并且恢复初期强光反而会加重光抑制程度。

Response of Chlorophyll Fluorescence Transient in Leaves of Tomato under Chilling Stress and Subsequent Recovery

In order to investigate the effects of chilling stress and subsequent recovery on photosystem II(PSII) reaction centers and acceptor side of PSII in tomato, a controlled experiment was conducted in artificial climate chamber of Jinggangshan University. Tomato (Solanum lycopersicum L. cv Zhongshu No.4) with 6-leaf stage was used for this experiment. Two treatments employed were: (1) control(CK): seedlings were cultured in artificial climate chamber with temperature range approximately 18?28℃, photosynthetic photo flux density (PPFD) approximately 600μmol?m?2?s?1, 12h photoperiod. (2) Chilling(CL): seedlings were transferred at the beginning of the photoperiod(7：00) to artificial climate box(ZRY-YY1000, Ningbo, China) with a 12h photoperiod and 200μmol?m?2?s?1 PPFD and temperature of 8℃. The CL treatment lasted 4 days and the plants were transferred at the beginning of the photoperiod(7：00) to the artificial climate chamber at normal temperature for 4 days. Throughout the experiment, chlorophyll fluorescence transient was examined in the youngest developmental leaf under chilling stress and subsequent recovery periods. The results showed that chilling reduced the photochemical efficiency and photosynthetic performance of PSII in tomato leaves, and induced photoinhibition. Chilling decreased the numbers of active PSII reaction centers per cross section(RC/CS) and the efficiency that a trapped electron can move further ahead of QA?(Ψo). Chilling also decreased the specific energy fluxes per cross section for absorption (ABS/CS), trapping(TRo/CS), electron transport(ETo/CS), and the quantum yield of electron transport beyond QA?(φEo), which suggested that chilling inhibited the photosynthetic electron transportation. At the same time, chilling also initiated defense mechanism: first, chilling induced the reversible inactivation of PSII reaction center and promoting heat dissipation to decrease of the absorption and transportation of light energy, and reduction the accumulation of excess excitation energy. Soon afterwards, chilling increased the capacity of PQ in the PSII receptor side to prevent the accumulation of excess excitation energy in PSII. In this study, chilling mainly inhibited PSII activity, but had little effect on PSI. The absorption of light energy by antenna pigment and the capture of light energy by PSII reaction centers were easier to recover than electron transfer, and high light would aggravate the degree of photoinhibition at the early stage of recovery.