Duarte André G, Katata Genki, Hoshika Yasutomo, Hossain Mohitul, Kreuzwieser Jürgen, Arneth Almut, Ruehr Nadine K
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; The University of Western Ontario, 1151 Richmond St., London, ON, N6A 3K7, Canada.
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; Japan Atomic Energy Agency, Ibaraki, Japan.
J Plant Physiol. 2016 Oct 20;205:57-66. doi: 10.1016/j.jplph.2016.08.012. Epub 2016 Sep 1.
The frequency and intensity of climatic extremes, such as heat waves, are predicted to increase globally, with severe implications for terrestrial carbon and water cycling. Temperatures may rise above critical thresholds that allow trees to function optimally, with unknown long-term consequences for forest ecosystems. In this context, we investigated how photosynthetic traits and the water balance in Douglas-fir are affected by exposure to three heat waves with temperatures about 12°C above ambient. Photosynthetic carboxylation efficiency (V) was mostly unaffected, but electron transport (J) and photosynthetic rates under saturating light (A) were strongly influenced by the heat waves, with lagging limitations on photosynthesis still being observed six weeks after the last heat wave. We also observed lingering heat-induced inhibitions on transpiration, minimum stomatal conductance, and night-time stomatal conductance (g). Results from the stomatal models used to calculate minimum stomatal conductance were similar to g and indicated changes in leaf morphology, e.g. stomatal occlusions and alterations in epicuticular wax. Our results show Douglas-fir's ability to restrict water loss following heat stress, but at the price of reduced photosynthetic performance. Such limitations indicate potential long-term restrictions that heat waves can impose on tree development and functioning under extreme climatic conditions.
预计诸如热浪等极端气候事件的频率和强度在全球范围内将会增加，这对陆地碳循环和水循环具有严重影响。气温可能会升至高于树木最佳功能温度的临界阈值，这对森林生态系统的长期影响尚不清楚。在此背景下，我们研究了花旗松暴露于比环境温度高约12°C的三次热浪中时，其光合特性和水分平衡是如何受到影响的。光合羧化效率（V）基本未受影响，但电子传递（J）和饱和光强下的光合速率（A）受到热浪的强烈影响，在最后一次热浪过后六周仍能观察到光合作用存在滞后限制。我们还观察到热浪对蒸腾作用、最小气孔导度和夜间气孔导度（g）的抑制作用持续存在。用于计算最小气孔导度的气孔模型结果与g相似，表明叶片形态发生了变化，例如气孔堵塞和表皮蜡质的改变。我们的结果表明，花旗松在热胁迫后具有限制水分流失的能力，但代价是光合性能下降。这些限制表明，在极端气候条件下，热浪可能会对树木的生长发育和功能产生潜在的长期限制。
