The leaves of ice plants store water in surface bladder-like cells.

   
  "Southern Africa is the headquarters of a vast and varied family, the mesembryanthemums…One species retains liquid in tiny bladders on the surface of each bloated leaf that glisten in the sunshine and so give it the name, apt though improbable in these sun-baked lands, of 'ice plant'." (Attenborough 1995:278)

 

"The aerial surfaces of the common or crystalline ice plant Mesembryanthemum crystallinum L., a halophytic, facultative crassulacean acid metabolism species, are covered with specialized trichome cells called epidermal bladder cells (EBCs). EBCs are thought to serve as a peripheral salinity and/or water storage organ to improve survival under high salinity or water deficit stress conditions. However, the exact contribution of EBCs to salt tolerance in the ice plant remains poorly understood. An M. crystallinum mutant lacking EBCs was isolated from plant collections mutagenized by fast neutron irradiation. Light and electron microscopy revealed that mutant plants lacked EBCs on all surfaces of leaves and stems. Dry weight gain of aerial parts of the mutant was almost half that of wild-type plants after 3 weeks of growth at 400 mM NaCl. The EBC mutant also showed reduced leaf succulence and leaf and stem water contents compared with wild-type plants. Aerial tissues of wild-type plants had approximately 1.5-fold higher Na+ and Cl– content than the mutant grown under 400 mM NaCl for 2 weeks. Na+ and Cl– partitioning into EBCs of wild-type plants resulted in lower concentrations of these ions in photosynthetically active leaf tissues than in leaves of the EBC-less mutant, particularly under conditions of high salt stress. Potassium, nitrate, and phosphate ion content decreased with incorporation of NaCl into tissues in both the wild type and the mutant, but the ratios of Na+/K+ and Cl–/ NO2 3 content were maintained only in the leaf and stem tissues of wild-type plants. The EBC mutant showed significant impairment in plant productivity under salt stress as evaluated by seed pod and seed number and average seed weight. These results clearly show that EBCs contribute to succulence by serving as a water storage reservoir and to salt tolerance by maintaining ion sequestration and homeostasis within photosynthetically active tissues of M. crystallinum." (Agarie et al. 2007:1957)

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A procumbent annual with a characteristic covering of glistening papil¬lae. Leaves 3-8 cm long, 5-20 mm broad, more or less spathulate, succulent. Flowers solitary, terminal, pinkish red; pedicel up to 11 cm long. Sepals 5, ovate, persistent. Petals linear, up to 2 cm long, longer than the sepals. Outer stamens petaloid staminodes. Capsule star shaped on dehiscing.

The ‘ice plant’ is cultivated in gardens for its thick glistening foliage and showy flowers which open in sunlight.

Introduced from southern and western Africa, Mesembryanthemum crystallinum is in cultivation as an ornamental. Its use to treat scurvy by sailors, its popularity as an ornamental potted plant aboard ships, and its occurrence in ballast dumps (as in Pennsylvania) were some of the means by which this species has become so widespread throughout the world. Gauchos in Argentina used it to treat venereal disease.

Plants annual to biennial. Stems trailing, dichotomously branched, to 1 m. Leaves sessile or petiolate; petiole, ± clasping; blade ovate to spatulate, flat, 2-20 cm, margins undulate. Inflorescences terminal or axillary, cymes; proximal bracts opposite, leaflike; distal bracts alternate, reduced; flowering profusely. Flowers 7-10 mm diam.; hypanthium aging red, round; calyx lobes 5, unequal; petals 20-40, connate into tube, white, aging pink; stamens 30. Capsules coarsely papillate. Seeds 200, rough with minute tubercles. 2n = 18.