Ecophysiologic investigations in the family of the Mesembryanthemaceae : Occurrence of a CAM and Ion Content.

Overnight accumulation of malate, citrate, and isocitrate in a large number of species of Mesembryanthemaceae grown under identical environmental conditions was studied. Of the 27 species investigated, 24 showed malate accumulation, which in 3 cases was accompanied by considerable overnight accumulation of citrate. In the leaves of the same plants, the Na+, K+, Cl-, SO42-, and PO43- contents were determined. Although the plants were not exposed to substrates of high NaCl content, they exhibited extraordinarily high levels of Na+ and Cl-. All plants accumulated, much more Na+ than K+. No readily discernible correlation between the amount of any particular ion and the extend of CAM was found. It is concluded that halophilism and CAM are widespread phenomena in the family of Mesembryanthemaceae that possess ecologic significance.