Wagner Johanna, Larcher Walter
Institut für Botanik der Universität, Sternwartestraße 15, A-6020, Innsbruck, Austria.
Oecologia. 1981 Aug;50(1):88-93. doi: 10.1007/BF00378798.
The influence of light intensity and temperature on the diurnal course and magnitude of CO gas exchange and on acid metabolism was studied in the laboratory with rooted rosettes of Sempervivum montanum collected at 2,200 m above sea level in the Central Alps. Under a temperature regime having a cool dark period and warm light period, S. montanum exhibited the time course of CO gas exchange typical of a CAM plant; the response was very distinct even when the plants were well-watered. At day temperatures of less than 10° C and at night temperatures greater than 35° C, S. montanum behaved like a C plant. Characteristic for S. montanum are a broad temperature optimum and a wide range of temperatures in which CO uptake in light is possible (-2° to 45° C). Dark fixation of CO is evident between-2° and 35° C, an apparent uptake of external CO, on the other hand, only as high as 20° C. Light saturation of CO uptake is reached at 60-80 W m while the rate of deacidification is nearly maximal at 40 W m. These results show that, due to their specific metabolism, CAM plants can be favored not only in xeric habitats, but also in heat stressed mountain habitats where the daily variation in temperature may be extreme.
在实验室中，利用从阿尔卑斯山中部海拔2200米处采集的山地长生草的带根莲座叶丛，研究了光照强度和温度对CO₂气体交换的日变化过程及幅度以及对酸代谢的影响。在具有凉爽黑暗期和温暖光照期的温度条件下，山地长生草呈现出景天酸代谢（CAM）植物典型的CO₂气体交换时间进程；即使植株充分浇水，这种响应也非常明显。在白天温度低于10℃和夜间温度高于35℃时，山地长生草表现得像C₃植物。山地长生草的特点是温度最适范围宽，且在较宽的温度范围内（-2℃至45℃）都能在光照下吸收CO₂。在-2℃至35℃之间CO₂的暗固定明显，另一方面，外部CO₂的明显吸收只在高达20℃时出现。CO₂吸收的光饱和在60 - 80 W m⁻²时达到，而脱酸速率在40 W m⁻²时几乎最大。这些结果表明，由于其特定的代谢方式，CAM植物不仅在干旱生境中具有优势，而且在温度日变化可能极端的热胁迫山地生境中也具有优势。
