塔克拉玛干沙漠南缘沙漠—绿洲过渡带植被盖度低，生态环境极其脆弱。疏叶骆驼刺(Alhagi sparsifolia Shap.)是过渡带的优势建群种，其在维护过渡带的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。本研究以疏叶骆驼刺为研究对象，开展温度和光照强度对疏叶骆驼刺的光系统II（PSII）的影响，期望回答荒漠植物疏叶骆驼刺在高温胁迫下PSII活性的敏感性；在弱光下形态及PSII的适应策略；弱光适应后暴露在正常光强下叶片PSII的响应特征。主要研究结果如下：
（2）在38 – 44℃条件下，胁迫时间为5 min和20 min时，疏叶骆驼刺叶荧光曲线无明显变化；胁迫时间为40 min，随着温度的升高其荧光强度降低，但并无K点出现，表明发生可逆性失活；在44℃下胁迫60 min时，出现明显K点，表明放氧复合体(OEC)受到损害，OEC的损坏会对电子链的传递产生抑制。因此，如果未来出现44℃的极端天气且存在时间超过60 min，可能将会对疏叶骆驼刺的正常生长造成严重损害。
|其他摘要||Plant growth and development processes were affected by the changes of external environment. The average global temperature has increased by approximately 0.6 ℃ over the past 100 years and is projected to continue to rise at a rapid rate, which will cause ecological responses of both flora and fauna. Climate warming would affect the structure and function of the ecological system, especially for the cold and arid regions, which are the most sensitive area to climate change. Light, is one of the most important environmental factors that regulate the development of the photosynthetic system in higher plants; as the source of energy for carbon fixation, light exhibits a regulatory function in plant growth. Under different light conditions, leaves develop various characteristics. However, these studies have focused on plants in rainforests; studies have been rarely conducted on typical desert plants grown under high irradiance conditions.
Alhagi sparsifolia Shap. is the primary vegetation in the forelands of the Taklamakan Desert which is characteristic of high temperature and light intensity. This species is of great importance to wind prevention and sand fixation in the transition zone. We conducted a temperature and light experiments in order to investigate (1) the sensitivity of photosystem II (PSII) activity in A. sparsifolia under brief elevated temperature; (2) shade adaptive strategy of morphology and PSII in A. sparsifolia under low light conditions; (3) response of PSII activity in A. sparsifolia to exposure to natural light after being kept in shade. Main results for this study are as follows:
(1) Both the activity and the density of the reaction centers in leaves were higher than that of assimilative branches at 35 – 48℃; leaves and assimilative branches have the same temperature sensitivity point; assimilative branches showed better adaptability than leaves of A. sparsifolia above 52 ℃, suggesting that assimilative branches might be more adaptive to severe environment.
(2) OJIP transients were only slightly changed at 5 and 20 min, but decreased with increasing temperature at 40 min with no apparent K-step, and indicate that they have recovery of activity of PSII. Moreover, the OJIP transients were limited by increasing timing stress, with a pronounced K-step at 44 ℃ for 60 min, and suggested that oxygen-evolving complex (OEC) was damaged and an inhibition of the electron donor to the secondary electron donor of PSII. Such conditions may result in the photoinhibition and metabolic impairment of A. sparsifolia at the southern Taklamakan Desert before its adaption to 44 ℃ which is transient elevation in air temperature under extreme weather conditions.
(3) Low-light conditions limited the normal growth of A. sparsifolia. The assimilative branches were disappeared in low irradiance (with higher soil water content) and maybe it is an evolution for greater productivity. The root to shoot ratios was decreased with decreasing light intensity. Plant would invest more energy in leaves for a greater efficiency in capturing light resources. These results were a trade-off adaption of A. sparsifolia for low light conditions.
(4) Leaves PSII activity was enhanced, however, the electron transport from donor side of PSII to acceptor side of PSI was inhibited at low light conditions. These results maybe caused the biomass accumulation reduced under low irradiance. A. sparsifolia was unable to cope with high-light intensities after 20 days of exposure to natural irradiance from low light condition. PSII activity of immature leaves was higher than that of mature leaves under low and normal light conditions. Moreover, immature leaves were more sensitive than mature leaves to light stress|
李磊. 温度与光强对疏叶骆驼刺表型可塑性及光系统II活性的影响[D]. 北京. 中国科学院大学,2015.