Chapter 10 Climate Change Responses and Adaptations in Crassulacean Acid Metabolism (CAM) Plants

Global climatic change is predicted to result in certain areas of the earth’s surface becoming hotter and drier. These spatially durable changes in climate will likely have negative impacts on the productivity of many plant species that are poorly adapted to increasing air:leaf vapor pressure deficits. However, more that 6% of vascular plants have evolved crassulacean acid metabolism (CAM) as a photosynthetic adaptation to hotter and drier climates. This specialized mode of photosynthesis exploits a temporal CO2 pump with nocturnal CO2 uptake and concentration to reduce photorespiration, improve water-use efficiency (WUE), and optimize the adaptability of plants to hotter and drier climates. CAM species have a suite of physiological and anatomical adaptations that make them resilient to extreme heat and high insolation including tissue succulence, water-storage and water-capture strategies to attenuate drought, and thick cuticles, epicuticular wax, low stomatal density, high stomatal responsiveness, UV-light protection, and shallow rectifier-like roots to limit water loss under conditions of water deficit. Various modeling approaches have been developed to estimate the growth potential of CAM species under current and future climatic conditions.