中科院揭示疏叶骆驼刺在不同温度和光照下光系统II活性的特征

光照和温度是影响植物生长的重要环境因子。疏叶骆驼刺(Alhagi sparsifolia Shap. )是塔克拉玛干沙漠南缘荒漠--绿洲过渡带上的主要建群种植物，在维持过渡带生态系统的结构和功能以及防风固沙方面发挥着重要的作用。

中国科学院新疆生态与地理研究所策勒国家站研究员李向义研究团队，通过控制实验，研究了策勒绿洲疏叶骆驼刺在不同高温条件和光照条件下的光系统II活性的特征。研究结果表明：在38-44℃条件下，当胁迫时间为5min和20min时，荧光曲线无明显变化;胁迫时间为40min，随着温度的升高荧光强度降低，但并无K点出现，表明发生可逆性失活;在44℃下胁迫60min时，出现明显K点，说明放氧复合体(OEC)受到损害，OEC的损坏会对电子链的传递产生抑制，表明在44℃下胁迫60min条件下会对疏叶骆驼刺造成不可逆性失活。因此，如果未来出现44℃的极端天气且存在时间超过60min的话，可能将会对疏叶骆驼刺的正常生长造成严重损害。

生长在高温强光照地区的荒漠植物疏叶骆驼刺一般被称之为典型的阳生植物，已有研究结果表明其能够适应一定的弱光环境，然而疏叶骆驼刺在一段时间的弱光驯化之后能否重新适应正常的光照条件尚不清楚。研究结果表明：疏叶骆驼刺在经过一段时间的弱光驯化后，将其暴露在正常光照下20天，骆驼刺植株的光系统II活性仍不能恢复到正常水平，因此，骆驼刺不能称之为典型的阳生植物。

原文摘要：

Effects of high temperature on the chlorophyll a fluorescence ofAlhagi sparsifolia at the southern Taklamakan Desert

Lei Li, Xiang-Yi Li, Xin-Wen Xu, Li-Sha Lin, Fan-Jiang Zeng

Climate change is expected to result in an increase in the frequency and magnitude of extreme weather events. Alhagi sparsifolia is an important factor for wind prevention and sand fixation in the forelands of the Taklamakan Desert. The effects of high temperature on desert plants remain widely unknown. In this work, chlorophyll a fluorescence induction kinetics were investigated at different time stresses of 5, 20, 40, and 60 min at temperature gradients of 38–44 °C at 2 °C intervals. A pronounced K-step was found, and the values of the maximum quantum yield for primary photochemistry, the quantum yield of electron transport, the density of reaction centers and the performance index on absorption basis were lowest after 60 min at 44 °C, thus indicating that the oxygen-evolving complex was damaged, the inactivated reaction centers increased, and the activity of the photosystem II (PSII) reaction center in leaves was seriously limited. Therefore, we suggest that under normal temperature (below 42 °C), the PSII of A. sparsifolia would be unaffected. When such temperature is maintained for 40 min, the activity of PSII would be limited, and when retained for 60 min, PSII may be severely damaged.

Photosystem II activity of typical desert plant Alhagi sparsifolia Sharp.: response to exposure to natural light after being kept in shade

Lei Li, Xiang-yi Li, Xin-wen Xu, Li-sha Lin, Fan-jiang Zeng, Feng-li Chen

Alhagi sparsifolia Sharp., commonly considered as a type of sun plant, is the main vegetation found in the forelands of Taklamakan desert; this plant has an important function in wind prevention and sand fixation at the transition zone. A. sparsifolia could adapt to shaded conditions after a period of exposure to low-light conditions. However, whether or not the sun plant A. sparsifolia can adapt to natural light intensity after initial exposure to shaded conditions remains unknown. The specific light adaptation mechanism of this species is yet to be identified. In this study, the characteristics of the photosystem II (PSII) of A. sparsifolia exposed to natural light after the initial treatment under shaded lighting conditions were examined. Our results indicated that the PSII activity of A. sparsifolia under the specified condition was low; the thickness of leaves was reduced and occurred as an adaptive response to capture high amounts of light and exhibit high intensity of light-use efficiency. Shade leaves differed in terms of chlorophyll. Furthermore, the excess excitation energy has been converted to thermal dissipation energy to maintain energy balance. Shade-grown plants cannot adapt to strong irradiance, which is normal in plants for a short period when they are initially maintained under low-light conditions. Therefore, A. sparsifolia should not be considered as a typical sun plant.

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