典型荒漠植物白刺叶绿素荧光特性对模拟增雨的响应

我国西北干旱区未来降水有增加趋势,研究不同增雨条件下典型荒漠植物白刺叶片叶绿素荧光变化规律能够揭示未来气候变化条件下荒漠植物对降水增加的响应与适应机制,对准确评估陆地生态系统碳收支具有重要意义。基于乌兰布和沙漠东缘白刺荒漠生态系统人工模拟增雨试验平台,除对照(自然降水)外,共设置4个增雨处理,即在自然降水的基础上分别增加多年平均降水量(145 mm)的25%、50%、75%和100%,分别测定不同增雨条件下白刺的叶绿素荧光参数。结果表明:1)增雨对白刺叶片叶绿素荧光特性有显著影响的时间主要在白刺自身生理活性强、生长速率快且对水分需求较高的生长季前期(6月);2)增雨后,原初光化学量子效率(F_v/F_m)、实际光化学量子效率(ΦPSⅡ)、电子传递速率(ETR)、光化学猝灭系数(q_p)和非光化学猝灭系数(nPq)上升,增雨使白刺叶片对光能的吸收、利用和转化效率提高的同时,也增加了其热耗散能力;3)原初光化学量子效率、电子传递速率和非光化学猝灭系数三者对最大净光合速率变化的解释量分别为29%、26%和23%,说明PSⅡ反应中心活...

Response of Chlorophyll Fluorescence Characteristics of a Typical Desert Plant Species Nitraria tangutorum to Simulated Rainfall Enhancement

There exists an increasing trend of the precipitation in the arid regions of Northwest China in the future.The study on the changes of chlorophyll fluorescence parameters of Nitraria tangutorum,a typical plant species in arid areas under different rain enhancement treatments can reveal the response and adaptation mechanism of desert plants to the increase of precipitation under future climate change conditions.And it is particularly important to accurately assess the carbon budget of terrestrial ecosystems.Based on the artificial simulated rainfall enhancement experiment platform of the desert ecosystem in Ulanbuhe Desert in Northwest China,in addition to the control(natural precipitation),four precipitation enhancement treatments(25%,50%,75%,and 100%increments of local mean annual precipitation,respectively)were set up.The chlorophyll fluorescence parameters of N.tangutorum were measured under different rainfall enhancement treatments.The results showed that:1)there were significant differences in chlorophyll fluorescence parameters of N.tangutorum leaves under different rainfall conditions,and the differences were significant in June when the plant presented strong physiological activity,fast growth rate and high water demand.2)After increasing rainfall,primary photochemical quantum efficiency(F v/F m),actual photochemical quantum efficiency(ФPSⅡ),electron transport rate(ETR),photochemical quenching(q p)and non photochemical quenching coefficient(n P q)of N.tangutorum leaves increased,which indicated that rain enhancement increased the efficiency of absorption,utilization and conversion light and the capacity of heat dissipation.3)Primary photochemistry quantum efficiency,electron transfer rate and non photochemical quenching coefficient were positively correlated with maximum net photosynthetic rate.The explanations of the three factors(F v/F m,ETR,and n P q)for maximum net photosynthetic rate were 29%,26%and 23%,respectively,which indicated that the increases of PSII reaction center activity,light energy conversion efficiency and electron transfer rate were the key processes to promote photosynthesis capacity and increase photosynthate accumulation of N.tangutorum.In a word,N.tangutorum showed strong acclimation to new water conditions,which was mainly reflected in regulating its physiological characteristics and increasing the accumulation of photosynthate.The results of this study are important for revealing the response mechanism of desert ecosystem to precipitation increase under the background of global change.