PATTERNS OF CARBON PARTITIONING IN LEAVES OF CRASSULACEAN ACID METABOLISM SPECIES DURING DEACIDIFICATION

Carbohydrates stored during deacidification in the light were examined in 11 Crassulacean acid metabolism (CAM) species from widely separate d taxa grown under uniform conditions. The hypothesis that NAD(P) mali c enzyme CAM species store chloroplastic starch and glucans, and phosp hoenolpyruvate carboxykinase species store extrachloroplastic sugars o r polymers was disproved. Of the six malic enzyme species examined, Ka lanchoe tubiflora, Kalanchoe pinnata, Kalanchoe daigremontiana, and Va nilla planifolia stored mainly starch. Sansevieria hahnii stored sucro se and Agave guadalajarana did not store starch, glucose, fructose, or sucrose. Of the five phosphoenolpyruvate carboxykinase species invest igated, Ananus comosus stored extrachloroplastic carbohydrate, but Sta pelia gigantea, Hoya carnosa, and Portea petropolitana stored starch, whereas Aloe vera stored both starch and glucose. Within families, the major decarboxylase was common for all species examined, whereas stor age carbohydrate could differ both between and within genera. In the B romeliaceae, A. comosus stored mainly fructose, but P. petropolitana s tored starch. In the genus Aloe, A. vera stored starch and glucose, bu t A. arborescens is known to store a galactomannan polymer. We postula te that the observed variation in carbohydrate partitioning between CA M species is the result of two principal components: (a) constraints i mposed by the CAM syndrome itself, and (b) diversity in biochemistry r esulting from different evolutionary histories.