Stem succulents are fleshy

succulent In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...

columnar shaped

plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

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 Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night. ...

, 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 reac ...

where the plants'

stomata In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

open to exchange gasses and fix CO2 almost exclusively at night. Their leaves are absent or highly reduced, instead forming protective spines or

thorns Thorn(s) or The Thorn(s) may refer to: Botany * Thorns, spines, and prickles, sharp structures on plants * ''Crataegus monogyna'', or common hawthorn, a plant species Comics and literature * Rose and Thorn, the two personalities of two DC Com ...

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 mouthpart ...

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 ''Euphorbia'' is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to t ...

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 Greek ...

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 (

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 ''Stapelia'' is a genus of low-growing, spineless, stem succulent plants, predominantly from South Africa with a few from other parts of Africa. Several Asian and Latin American species were formerly included but they have all now been transfe ...

References

{{reflist Succulent plants Plant morphology Desert flora