Institute of Botany, Technical University of Darmstadt, Schnittspahnstrasse 3-5, D-64287 Darmstadt, Germany.
AoB Plants. 2010;2010:plq005. doi: 10.1093/aobpla/plq005. Epub 2010 May 13.
Single stressors such as scarcity of water and extreme temperatures dominate the struggle for life in severely dry desert ecosystems or cold polar regions and at high elevations. In contrast, stress in the tropics typically arises from a dynamic network of interacting stressors, such as availability of water, CO(2), light and nutrients, temperature and salinity. This requires more plastic spatio-temporal responsiveness and versatility in the acquisition and defence of ecological niches.
The mode of photosynthesis of crassulacean acid metabolism (CAM) is described and its flexible expression endows plants with powerful strategies for both acclimation and adaptation. Thus, CAM plants are able to inhabit many diverse habitats in the tropics and are not, as commonly thought, successful predominantly in dry, high-insolation habitats.
Typical tropical CAM habitats or ecosystems include exposed lava fields, rock outcrops of inselbergs, salinas, savannas, restingas, high-altitude páramos, dry forests and moist forests.
Morphotypical and physiotypical plasticity of CAM phenotypes allow a wide ecophysiological amplitude of niche occupation in the tropics. Physiological and biochemical plasticity appear more responsive by having more readily reversible variations in performance than do morphological adaptations. This makes CAM plants particularly fit for the multi-factor stressor networks of tropical forests. Thus, while the physiognomy of semi-deserts outside the tropics is often determined by tall succulent CAM plants, tropical forests house many more CAM plants in terms of quantity (biomass) and quality (species diversity).
在严重干旱的沙漠生态系统或寒冷的极地地区以及高海拔地区，单一的胁迫因素，如水资源短缺和极端温度，主导着生命的斗争。相比之下，热带地区的压力通常来自于相互作用的胁迫因素的动态网络，如水分、CO(2)、光照和养分、温度和盐度的可用性。这需要在生态位的获取和防御方面具有更具弹性的时空响应能力和多功能性。
描述了景天酸代谢（CAM）的光合作用模式，其灵活的表达赋予了植物适应和适应的强大策略。因此，CAM 植物能够栖息在热带地区的许多不同栖息地，而不像人们通常认为的那样，主要成功于干燥、高光照的栖息地。
热带 CAM 栖息地：典型的热带 CAM 栖息地或生态系统包括暴露的熔岩流、孤岛的岩石露头、盐沼、稀树草原、休息地、高海拔的帕拉莫、干燥森林和湿润森林。
CAM 的形态和生理可塑性：CAM 表型的形态和生理可塑性允许在热带地区占据广泛的生态生理幅度。生理和生化可塑性似乎更具响应性，因为它们的性能变化更易于逆转，而形态适应则不然。这使得 CAM 植物特别适合热带森林的多因素胁迫网络。因此，虽然半沙漠地区的外貌往往由高大多汁的 CAM 植物决定，但就数量（生物量）和质量（物种多样性）而言，热带森林中存在着更多的 CAM 植物。
