Crassulacean Acid Metabolism is an intriguing photosynthetic pathway that interacts with a number of environmental factors including water stress. The general objective of this proposal is to understand the compartmentation and regulation of mitochondrial malic acid metabolism in succulent plants with Crassulacean Acid Metabolism (CAM). Specifically, regulation of malic acid metabolism in mitochondria during acidification and deacidification will be examined using in vivo tracer flux analysis and in vitro studies of mitochondrial metabolism. On-line methods for monitoring 18O fractionation will be developed to determine the importance of the alternative respiration pathway for malate fluxes during the CAM process. This research will improve understanding of the physiological regulation of CAM metabolism, a biochemical pathway that apparently helps certain plant species respond to environmental stress. The results will also be applicable to other physiological processes in which malic acid plays a key role such as generation of osmotic pressure during stomatal opening and ionic balance during nutrient uptake and incorporation. Finally this research will develop direct measurements of alternative pathway respiration, a key physiological response thought to provide plants with flexibility in the face of environmental fluctuation.
