Abstract
Both laboratory- and field-grown M. crystallinum plants exhibited large scale diurnal ion fluctuations. In mesophyll tissue, K and Na levels varied in conjunction with acid levels while chloride levels varied in opposition. Thus, dark CO2 fixation in this crassulacean acid metabolism species seems analogous to the common plant process of malate synthesis to balance cation surplus. Na levels in the epidermis appeared to fluctuate in opposition to those in the mesophyll. Inorganic cations may cycle between mesophyll and epidermal tissue to balance malate accumulation and to produce stomatal opening in the dark.