Loik Michael E, Harte John
Department of Biology, California State University, 5500 University Parkway, 92407-2397, San Bernardino, CA, USA.
Energy and Resources Group, University of California, Room 100, Building T-4, 94720, Berkeley, CA, USA.
Oecologia. 1996 Oct;108(2):224-231. doi: 10.1007/BF00334645.
Leaf tolerance to high temperatures, as determined by electrolyte leakage and chlorophyll a fluorescence, was compared for Artemisia tridentata (Asteraceae), a widespread shrub of the Great Basin, Colorado Plateau, and western slope of the Rocky Mountains, and Potentilla gracilis (Rosaceae), a herbaceous forb common to high-elevation meadows of the western United States. Species-specific and treatment-specific differences in leaf temperature, high-temperature tolerance and chlorophyll a fluorescence from photosystem II were compared, to test the hypothesis that plants at ecosystem borders will exhibit species-specific responses to climate change. Measurements were made for plants exposed to a climate change warming manipulation on a major ecosystem border at the Rocky Mountain Biological Laboratory, Colorado, United States, in July and August 1995. In July, daily maximal leaf temperatures were significantly higher for P. gracilis than for A. tridentata. Leaf temperatures were slightly lower in August than July for leaves of both species, on control and heated plots, despite the fact that daily maximum air temperatures were not significantly different for the two months. High-temperature tolerance was determined for leaves treated for 1 h at temperatures ranging from 15°C to 65°C. LT was approximately 46°C for both species on control plots, but was 43°C for leaves of both species from heated plots, contrary to the predictions of the hypothesis. No shift in LT (acclimation) was apparent between July and August. Changes in chlorophyll a fluorescence from photosystem II (F /F ) were used to characterize the photosynthetic response to high temperatures. For both A. tridentata and P. gracilis in July, F /F was about 0.7, but decreased for temperatures above 40°C. The results suggest that plant responses to global warming at ecosystem borders may be influenced by factors other than leaf-level physiological tolerance to elevated temperatures.
通过电解质渗漏和叶绿素a荧光测定，比较了三齿蒿（菊科）和纤细委陵菜（蔷薇科）叶片对高温的耐受性。三齿蒿是大盆地、科罗拉多高原和落基山脉西坡广泛分布的一种灌木，纤细委陵菜是美国西部高海拔草甸常见的一种草本植物。比较了叶片温度、高温耐受性以及光系统II中叶绿素a荧光的种间差异和处理间差异，以检验生态系统边界处的植物对气候变化会表现出种特异性反应这一假设。1995年7月和8月，在美国科罗拉多州落基山生物实验室的一个主要生态系统边界上，对暴露于气候变化变暖处理的植物进行了测量。7月，纤细委陵菜的日最高叶片温度显著高于三齿蒿。在对照和加热地块上，两个物种的叶片8月的温度略低于7月，尽管这两个月的日最高气温没有显著差异。在15℃至65℃的温度范围内对叶片处理1小时，测定其高温耐受性。对照地块上两个物种的致死温度（LT）约为46℃，但加热地块上两个物种叶片的致死温度为43℃，这与假设的预测相反。7月和8月之间，致死温度（驯化）没有明显变化。用光系统II中叶绿素a荧光的变化（F /F ）来表征对高温的光合反应。7月，三齿蒿和纤细委陵菜的F /F 约为0.7，但温度高于40℃时该值下降。结果表明，生态系统边界处植物对全球变暖的反应可能受叶片对温度升高的生理耐受性以外的因素影响。
