Deacidification in a plant with crassulacean acid metabolism associated with anion-cation balance

Abstract

In plant tissues using crassulacean acid metabolism (CAM), malate accumulates during the dark and declines in the subsequent light period. The malate is an intermediate store of CO₂ which is fixed photosynthetically during the subsequent day and for CAM plants the amplitude of the fluctuation is significant for plant carbon assimilation¹. Because they are so considerable, the maximum values for acid content aroused early comment². The maximum seems to be related not just to the rate of acidification but also to internal factors which may include the water and cation content of tissues³. Changes in the distribution of cations have recently been linked to the diel fluctuation in malate⁴. I report here that the malate measured in leaves at the end of the day can be correlated with an imbalance between total cations and the organic acids other than malate in the leaves of Kalanchoe daigremontiana. There occurs a greater imbalance in leaves of plants grown in a long compared with a short day and this may explain the finding that leaves contain considerably more malate at the end of a long photoperiod.