Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.
N.M. Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Moscow, Russia.
Photosynth Res. 2019 Mar;139(1-3):203-214. doi: 10.1007/s11120-018-0535-7. Epub 2018 Jun 20.
In this work, we have compared photosynthetic characteristics of photosystem II (PSII) in Tradescantia leaves of two contrasting ecotypes grown under the low light (LL) and high light (HL) regimes during their entire growth period. Plants of the same genus, T. fluminensis (shade-tolerant) and T. sillamontana (sun-resistant), were cultivated at 50-125 µmol photons m s (LL) or at 875-1000 µmol photons m s (HL). Analyses of intrinsic PSII efficiency was based on measurements of fast chlorophyll (Chl) a fluorescence kinetics (the OJIP test). The fluorescence parameters F/F (variable fluorescence) and F (the initial level of fluorescence) in dark-adapted leaves were used to quantify the photochemical properties of PSII. Plants of different ecotypes showed different sustainability with respect to changes in the environmental light intensity and temperature treatment. The sun-resistant species T. sillamontana revealed the tolerance to variations in irradiation intensity, demonstrating constancy of maximum quantum efficiency of PSII upon variations of the growth light. In contrast to T. sillamontana, facultative shade species T. fluminensis demonstrated variability of PSII photochemical activity, depending on the growth light intensity. The susceptibility of T. fluminensis to solar stress was documented by a decrease in F/F and a rise of F during the long-term exposition of T. fluminensis to HL, indicating the loss of photochemical activity of PSII. The short-term (10 min) heat treatment of leaf cuttings caused inactivation of PSII. The temperature-dependent heating effects were different in T. fluminensis and T. sillamontana. Sun-resistant plants T. sillamontana acclimated to LL and HL displayed the same plots of F/F versus the treatment temperature (t), demonstrating a decrease in F/F at t ≥ 45 °C. The leaves of shadow-tolerant species T. fluminensis grown under the LL and HL conditions revealed different sensitivities to heat treatment. Plants grown under the solar stress conditions (HL) demonstrated a gradual decline of F/F at lower heating temperatures (t ≥ 25 °C), indicating the "fragility" of their PSII as compared to T. fluminensis grown at LL. Different responses of sun and shadow species of Tradescantia to growth light and heat treatment are discussed in the context of their biochemical and ecophysiological properties.
在这项工作中，我们比较了在整个生长过程中，在低光（LL）和高光（HL）条件下生长的两种 contrasting 生态型的 Tradescantia 叶片中的光系统 II（PSII）的光合作用特性。同一属的 T. fluminensis（耐荫）和 T. sillamontana（耐阳光）植物分别在 50-125 μmol 光子 m s（LL）或 875-1000 μmol 光子 m s（HL）下培养。基于快速叶绿素（Chl）a 荧光动力学（OJIP 测试）测量分析了 PSII 的固有效率。暗适应叶片中的荧光参数 F/F（可变荧光）和 F（荧光的初始水平）用于量化 PSII 的光化学特性。不同生态型的植物对环境光强和温度处理的变化表现出不同的可持续性。耐阳光的物种 T. sillamontana 显示出对辐射强度变化的耐受性，表明在生长光变化时 PSII 的最大量子效率保持恒定。与 T. sillamontana 相反，兼性荫蔽种 T. fluminensis 表现出 PSII 光化学活性的可变性，这取决于生长光的强度。T. fluminensis 对太阳胁迫的敏感性通过 F/F 和 F 在长期暴露于 HL 期间的降低来记录，表明 PSII 的光化学活性丧失。叶片切割的短期（10 分钟）热处理会使 PSII 失活。T. fluminensis 和 T. sillamontana 中存在不同的温度依赖性加热效应。适应 LL 和 HL 的耐阳光植物 T. sillamontana 显示出 F/F 与处理温度（t）的相同关系图，表明在 t≥45°C 时 F/F 降低。在 LL 和 HL 条件下生长的耐荫物种 T. fluminensis 的叶片对热处理表现出不同的敏感性。在太阳胁迫条件（HL）下生长的植物在较低的加热温度（t≥25°C）下表现出 F/F 的逐渐下降，这表明与在 LL 下生长的 T. fluminensis 相比，它们的 PSII 逐渐变弱。在生长光和热处理方面，Tradescantia 的阳性和阴性物种的不同反应在它们的生化和生态生理特性的背景下进行了讨论。
