Mesembryanthemum crystallinum is covered with enlarged epidermal cells, called "bladder cells". The main function of these bladder cells is to reserve water. It flowers from spring to early summer. Flowers open in the morning and close at night, and are insect pollinated. It can be annual, biennial or perennial, but its life cycle is usually completed within several months, depending on environmental conditions.
Habitat
Mesembryanthemum crystallinum is found on a wide range of soil types, from well-drained sandy soils, to loamy and clay soils. It can tolerate nutritionally poor or saline soils. As with many introduced species it also grows in disturbed sites such as roadsides, rubbish dumps and homestead yards.
Biology
The plant usually uses C3 carbon fixation, but when it becomes water- or salt-stressed, it is able to switch to Crassulacean acid metabolism. Like many salt-tolerant plants, M. crystallinum accumulates salt throughout its life, in a gradient from the roots to the shoots, with the highest concentration stored in epidermal bladder cells. The salt is released by leaching once the plant dies. This results in a detrimental osmotic environment preventing the growth of other, non-salt-tolerant species while allowing M. crystallinum seeds to germinate. In M. crystallinum, the number of seeds produced depends on whether CAM has been activated and the size the plant has grown to in its juvenile growth phase. During seed production, older portions of the plant progressively die off and dry out. The developing seed capsules continue to sequester salt and produce viable seeds. Seeds at the top of the capsule generally germinate immediately on imbibation while seeds at the base may remain dormant for longer than four weeks.
History
The plant was once promoted in the United States and Europe as a vegetable, but failed to gain popularity.
Uses
Its leaves are edible, as with some other members of the family Aizoaceae. In southern Africa, the leaves and stems are gathered from the wild and pickled. Ice plants are also used in South Africa as a way of deterring fires, or "firescaping" gardens. Seeds can also be eaten. The crushed leaves can be used as a soap substitute and has some medicinal uses. It is rarely, if ever, grazed upon by domestic stock. It is also cultivated for ornamentation. Due to its salt accumulation, M. crystallinum may be useful for bio-remediation.
