Stem succulents are fleshy succulent columnar shaped

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

which conduct photosynthesis mainly through their stems rather than their leaves.Frerea indica, a Stem Succulent CAM Plant with Deciduous C₃ Leaves, Otto L. Lange and Margit Zuber, Oecologia, Vol. 31, No. 1 (1977), pp. 67-72, Published by: Springer

/ref>Stem Succulent, Encyclopædia Britannica
/ref>Stem Succulents, Map of Life
/ref> These plants are defined by their succulent stems and have evolved to have similar forms by

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

to occupy similar niches.

Description

Stem succulents are succulent plants defined by their succulent stems, which function to store water and conduct

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

. These plants, like many others native to hot dessert regions, undergo CAM photosynthesis, an alternative

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical ...

where the plants' stomata open to exchange gasses and fix CO2 almost exclusively at night. Their leaves are absent or highly reduced, instead forming protective spines or thorns to deter

herbivores A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

and collect drip condensed water vapor at night.Shoot Stem Modifications, Encyclopædia Britannica
/ref> Stem succulents are related by form, but not by evolution. They evolved to have similar forms and physiological characteristics by

. Examples are tall thin Euphorbias from deserts and arid regions of southern African and Madagascar, similarly shaped

cacti A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gree ...

from North America and South America, which occupy a similar

xeric Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (ancient Greek xērós, “dry") shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this h ...

evolutionary niche, and members of two genera of the family

Asclepiadaceae The Asclepiadoideae are a subfamily of plants in the family Apocynaceae. Formerly, they were treated as a separate family under the name Asclepiadaceae, e.g. by APG II, and known as the milkweed family. They form a group of perennial herbs, tw ...

(

Hoodia ''Hoodia'' (; known locally as "ghaap" or "bobbejaanghaap") is a genus of flowering plants in the family Apocynaceae, under the subfamily Asclepiadoideae, native to Southern Africa. One species of ''Hoodia'' in particular, '' Hoodia gordonii' ...

and Stapelia).

References

{{reflist Succulent plants Plant morphology Desert flora