Stem succulents are succulent plants defined by their succulent stems, which function to store water and conduct
photosynthesis. These plants, like many others native to hot desert regions, undergo
CAM photosynthesis, an alternative
metabolic pathway where the plants'
stomata open to exchange gasses and fix almost exclusively at night. Stem succulents are related by form, but not by evolution. They evolved to have similar forms and physiological characteristics by
convergent evolution. Examples are tall thin
Euphorbias from deserts and arid regions of southern African and Madagascar, similarly shaped
cacti from North America and South America, which occupy a similar
xeric evolutionary niche, and members of two genera of the family
Asclepiadaceae (
Hoodia and
Stapelia). ==References==