Crassulacean acid metabolism, also known as CAM photosynthesis, is a

carbon fixation Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and a ...

pathway that evolved in some

plant 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 ...

s as an adaptation to

arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most a ...

conditions that allows a plant to

photosynthesize 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 in ...

during the day, but only exchange gases at night. In a plant using full CAM, the

stoma 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 ...

ta in the leaves remain shut during the day to reduce

evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpira ...

, but they open at night to collect carbon dioxide () and allow it to diffuse into the

mesophyll cell A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

s. The is stored as four-carbon

malic acid Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L ...

vacuoles A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic m ...

at night, and then in the daytime, the malate is transported to chloroplasts where it is converted back to , which is then used during photosynthesis. The pre-collected is concentrated around the enzyme

RuBisCO Ribulose-1,5-bisphosphate carboxylase-oxygenase, commonly known by the abbreviations RuBisCo, rubisco, RuBPCase, or RuBPco, is an enzyme () involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is c ...

, increasing photosynthetic efficiency. This mechanism of acid metabolism was first discovered in plants of the family

Crassulaceae The Crassulaceae (from Latin ''crassus'', thick), also known as the stonecrop family or the orpine family, are a diverse family of dicotyledon flowering plants characterized by succulent leaves and a unique form of photosynthesis, known as Crassu ...

Historical background

Observations relating to CAM were first made by de Saussure in 1804 in his ''Recherches Chimiques sur la Végétation''. Benjamin Heyne in 1812 noted that ''Bryophyllum'' leaves in India were acidic in the morning and tasteless by afternoon. These observations were studied further and refined by Aubert, E. in 1892 in his ''Recherches physiologiques sur les plantes grasses'' and expounded upon by Richards, H. M. 1915 in ''Acidity and Gas Interchange in Cacti'', Carnegie Institution. The term CAM may have been coined by Ranson and Thomas in 1940, but they were not the first to discover this cycle. It was observed by the

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

s Ranson and Thomas, in the

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 ...

family

(which includes jade plants and ''

Sedum ''Sedum'' is a large genus of flowering plants in the family Crassulaceae, members of which are commonly known as stonecrops. The genus has been described as containing up to 600 species, subsequently reduced to 400–500. They are leaf succule ...

''). The name "Crassulacean acid metabolism" refers to acid metabolism in Crassulaceae, and not the

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cel ...

of "crassulacean acid"; there is no chemical by that name.

Overview: a two-part cycle

CAM is an adaptation for increased efficiency in the use of water, and so is typically found in plants growing in arid conditions. (CAM is found in over 99% of the known 1700 species of ''

Cactaceae 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 ...

'' and in nearly all of the cactii producing edible fruits.)

During the night

During the night, a plant employing CAM has its stomata open, allowing to enter and be fixed as organic acids by a PEP reaction similar to the pathway. The resulting organic acids are stored in

vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...

s for later use, as the

Calvin cycle The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...

cannot operate without ATP and

NADPH Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NAD ...

, products of

light-dependent reactions Light-dependent reactions is jargon for certain photochemical reactions that are involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions, the first occurs at photosystem II (PSII) and ...

that do not take place at night. CAMplantgraph

During the day

During the day, the stomata close to conserve water, and the -storing organic acids are released from the vacuoles of the mesophyll cells. An enzyme in the stroma of

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s releases the , which enters into the Calvin cycle so that

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 in ...

may take place.

Benefits

The most important benefit of CAM to the plant is the ability to leave most leaf stomata closed during the day. Plants employing CAM are most common in arid environments, where water is scarce. Being able to keep stomata closed during the hottest and driest part of the day reduces the loss of water through

, allowing such plants to grow in environments that would otherwise be far too dry. Plants using only carbon fixation, for example, lose 97% of the water they take up through the roots to transpiration - a high cost avoided by plants able to employ CAM.

Comparison with metabolism

The pathway bears resemblance to CAM; both act to concentrate around

, thereby increasing its efficiency. CAM concentrates it temporally, providing during the day, and not at night, when respiration is the dominant reaction. plants, in contrast, concentrate spatially, with a RuBisCO reaction centre in a "

bundle sheath A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in the stem, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will includ ...

cell" being inundated with . Due to the inactivity required by the CAM mechanism, carbon fixation has a greater efficiency in terms of PGA synthesis. There are some /CAM intermediate species, such as '' Peperomia camptotricha'', ''

Portulaca oleracea ''Portulaca oleracea'' (common purslane, also known as little hogweed, or pursley) is an annual (actually tropical perennial in USDA growing zones 10–11) succulent in the family Portulacaceae. Description The plant may reach in height. It ...

'', and

Portulaca grandiflora ''Portulaca grandiflora'' is a succulent flowering plant in the family Portulacaceae, native to southern Brazil, Argentina, and Uruguay and often cultivated in gardens.Huxley, A., ed. (1992). ''New RHS Dictionary of Gardening''. Macmillan . It h ...

. The two pathways of photosynthesis can occur in the same leaves but not in the same cells, and the two pathways cannot couple and can only occur side by side

Biochemistry

Plants with CAM must control storage of and its reduction to branched carbohydrates in space and time. At low temperatures (frequently at night), plants using CAM open their stomata, molecules diffuse into the spongy mesophyll's intracellular spaces and then into the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. Th ...

. Here, they can meet

phosphoenolpyruvate Phosphoenolpyruvate (2-phosphoenolpyruvate, PEP) is the ester derived from the enol of pyruvate and phosphate. It exists as an anion. PEP is an important intermediate in biochemistry. It has the highest-energy phosphate bond found (−61.9 kJ/m ...

(PEP), which is a

phosphorylated In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, whi ...

triose A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses (including dihydroxyacetone): L-glyceraldehyde and D-glyceraldehyde, the two enantiomers of glyceraldehyde, which are aldotriose ...

. During this time, the plants are synthesizing a protein called PEP carboxylase

kinase In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule dona ...

(PEP-C kinase), whose expression can be inhibited by high temperatures (frequently at daylight) and the presence of

malate Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L ...

. PEP-C kinase phosphorylates its target

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...

PEP carboxylase (PEP-C). Phosphorylation dramatically enhances the enzyme's capability to

catalyze Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the formation of

oxaloacetate Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound with the chemical formula HO2CC(O)CH2CO2H. Oxaloacetic acid, in the form of its conjugate base oxaloacetate, is a metabolic intermediate in many processe ...

, which can be subsequently transformed into

by NAD⁺

malate dehydrogenase Malate dehydrogenase () (MDH) is an enzyme that reversibly catalyzes the oxidation of malate to oxaloacetate using the reduction of NAD+ to NADH. This reaction is part of many metabolic pathways, including the citric acid cycle. Other malate ...

. Malate is then transported via malate shuttles into the vacuole, where it is converted into the storage form

. In contrast to PEP-C kinase, PEP-C is synthesized all the time but almost inhibited at daylight either by

dephosphorylation In biochemistry, dephosphorylation is the removal of a phosphate (PO43−) group from an organic compound by hydrolysis. It is a reversible post-translational modification. Dephosphorylation and its counterpart, phosphorylation, activate and deact ...

via PEP-C

phosphatase In biochemistry, a phosphatase is an enzyme that uses water to cleave a phosphoric acid monoester into a phosphate ion and an alcohol. Because a phosphatase enzyme catalyzes the hydrolysis of its substrate, it is a subcategory of hydrolases. P ...

or directly by binding malate. The latter is not possible at low temperatures, since malate is efficiently transported into the vacuole, whereas PEP-C kinase readily inverts dephosphorylation. In daylight, plants using CAM close their guard cells and discharge malate that is subsequently transported into chloroplasts. There, depending on plant species, it is cleaved into

pyruvate Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic ac ...

and either by

malic enzyme Malic enzyme may refer to '' decarboxylating'' malate dehydrogenases: * Malate dehydrogenase (decarboxylating) () or NAD-malic enzyme * Malate dehydrogenase (oxaloacetate-decarboxylating) (), another NAD-malic enzyme * Malate dehydrogenase (oxal ...

or by

PEP carboxykinase Phosphoenolpyruvate carboxykinase (, PEPCK) is an enzyme in the lyase family used in the metabolic pathway of gluconeogenesis. It converts oxaloacetate into phosphoenolpyruvate and carbon dioxide. It is found in two forms, cytosolic and mitoch ...

. is then introduced into the Calvin cycle, a coupled and self-recovering enzyme system, which is used to build branched carbohydrates. The by-product pyruvate can be further degraded in the

mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is use ...

citric acid cycle The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and protei ...

, thereby providing additional molecules for the Calvin Cycle. Pyruvate can also be used to recover PEP via

pyruvate phosphate dikinase Pyruvate, phosphate dikinase, or PPDK () is an enzyme in the family of transferases that catalyzes the chemical reaction :ATP + pyruvate + phosphate \rightleftharpoons AMP + phosphoenolpyruvate + diphosphate This enzyme has been studied primar ...

, a high-energy step, which requires ATP and an additional

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...

. During the following cool night, PEP is finally exported into the cytoplasm, where it is involved in fixing carbon dioxide via malate.

Use by plants

Plants use CAM to different degrees. Some are "obligate CAM plants", i.e. they use only CAM in photosynthesis, although they vary in the amount of they are able to store as organic acids; they are sometimes divided into "strong CAM" and "weak CAM" plants on this basis. Other plants show "inducible CAM", in which they are able to switch between using either the or mechanism and CAM depending on environmental conditions. Another group of plants employ "CAM-cycling", in which their stomata do not open at night; the plants instead recycle produced by

respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellula ...

as well as storing some during the day. Plants showing inducible CAM and CAM-cycling are typically found in conditions where periods of water shortage alternate with periods when water is freely available. Periodic drought – a feature of semi-arid regions – is one cause of water shortage. Plants which grow on trees or rocks (as

epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...

s or

lithophyte Lithophytes are plants that grow in or on rocks. They can be classified as either epilithic (or epipetric) or endolithic; epilithic lithophytes grow on the surfaces of rocks, while endolithic lithophytes grow in the crevices of rocks (and are also ...

s) also experience variations in water availability. Salinity, high light levels and nutrient availability are other factors which have been shown to induce CAM. Since CAM is an adaptation to arid conditions, plants using CAM often display other

xerophytic A xerophyte (from Greek ξηρός ''xeros'' 'dry' + φυτόν ''phuton'' 'plant') is a species of plant that has adaptations to survive in an environment with little liquid water, such as a desert such as the Sahara or places in the Alps or the ...

characters, such as thick, reduced leaves with a low surface-area-to-volume ratio; thick

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

; and stomata sunken into pits. Some shed their leaves during the dry season; others (the succulents) store water in

s. CAM also causes taste differences: plants may have an increasingly sour taste during the night yet become sweeter-tasting during the day. This is due to malic acid being stored in the vacuoles of the plants' cells during the night and then being used up during the day.

Aquatic CAM

CAM photosynthesis is also found in aquatic species in at least 4 genera, including: ''

Isoetes ''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...

'', ''

Crassula ''Crassula'' is a genus of succulent plants containing about 200 accepted species, including the popular jade plant ('' Crassula ovata''). They are members of the stonecrop family (Crassulaceae) and are native to many parts of the globe, but cult ...

'', '' Littorella'', ''

Sagittaria ''Sagittaria'' is a genus of about 303. Sagittaria Linnaeus
''

Vallisneria ''Vallisneria'' (named in honor of Antonio Vallisneri) is a genus of freshwater aquatic plant, commonly called eelgrass, tape grass or vallis. The genus is widely distributed in tropical and subtropical regions of Asia, Africa, Europe, and North ...

'', being found in a variety of species e.g. '' Isoetes howellii'', '' Crassula aquatica''. These plants follow the same nocturnal acid accumulation and daytime deacidification as terrestrial CAM species. However, the reason for CAM in aquatic plants is not due to a lack of available water, but a limited supply of . is limited due to slow diffusion in water, 10000x slower than in air. The problem is especially acute under acid pH, where the only inorganic carbon species present is , with no available bicarbonate or carbonate supply. Aquatic CAM plants capture carbon at night when it is abundant due to a lack of competition from other photosynthetic organisms. This also results in lowered ''

photorespiration Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The desired reaction i ...

'' due to less photosynthetically generated oxygen. Aquatic CAM is most marked in the summer months when there is increased competition for , compared to the winter months. However, in the winter months CAM still has a significant role.

Ecological and taxonomic distribution of CAM-using plants

The majority of plants possessing CAM are either

s (e.g., orchids, bromeliads) or succulent

xerophyte A xerophyte (from Greek ξηρός ''xeros'' 'dry' + φυτόν ''phuton'' 'plant') is a species of plant that has adaptations to survive in an environment with little liquid water, such as a desert such as the Sahara or places in the Alps or the ...

s (e.g., cacti, cactoid ''Euphorbia''s), but CAM is also found in

hemiepiphyte A hemiepiphyte is a plant that spends part of its life cycle as an epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debr ...

s (e.g., ''

Clusia ''Clusia'' is the type genus of the plant family Clusiaceae. Comprising 300-400 species, it is native to the tropics of the Americas. The genus is named by Carl Linnaeus in honor of the botanist Carolus Clusius. The closest relatives of ''Cl ...

'');

s (e.g., ''

'', ''

Sempervivum ''Sempervivum'' (Brit. , U.S. �sɛ̃mpeɹ'vivũm is a genus of about 40 species of flowering plants in the family Crassulaceae, commonly known as houseleeks. Other common names include liveforever (the source of the taxonomical designation ''Se ...

''); terrestrial bromeliads; wetland plants (e.g., ''

'', ''

'' (''Tillaea''), ''

Lobelia ''Lobelia'' () is a genus of flowering plants comprising 415 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions.Huxley, A., ed. (1992 ...

''; and in one

halophyte A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. Th ...

, ''

Mesembryanthemum crystallinum ''Mesembryanthemum crystallinum'' is a prostrate succulent plant native to Africa, Sinai and southern Europe, and naturalized in the New World. The plant is covered with large, glistening bladder cells or water vesicles, reflected in its common ...

''; one non-succulent terrestrial plant, (''

Dodonaea viscosa ''Dodonaea viscosa'', also known as the broadleaf hopbush, is a species of flowering plant in the ''Dodonaea'' (hopbush) genus that has a cosmopolitan distribution in tropical, subtropical and warm temperate regions of Africa, the Americas, south ...

'') and one

mangrove A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in sever ...

associate (''

Sesuvium portulacastrum ''Sesuvium portulacastrum'' is a sprawling perennial herb that grows in coastal areas throughout much of the world. It is commonly known as shoreline purslane or (ambiguously) " sea purslane," in English, ''dampalit'' in Tagalog and 海马齿sl ...

''). The only trees that can do CAM are in the genus ''

''; species of which are found across

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. C ...

, South America and the

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean S ...

. In ''

'', CAM is found in species that inhabit hotter, drier ecological niches, whereas species living in cooler montane forests tend to be . In addition, some species of ''

'' can temporarily switch their photosynthetic physiology from to CAM, a process known as facultative CAM. This allows these trees to benefit from the elevated growth rates of photosynthesis, when water is plentiful, and the drought tolerant nature of CAM, when the dry season occurs. Plants which are able to switch between different methods of carbon fixation include ''

Portulacaria afra ''Portulacaria afra'' (known as elephant bush, porkbush, purslane tree and ' in Afrikaans) is a small-leaved succulent plant found in South Africa. These succulents commonly have a reddish stem and leaves that are green, but also a variegated cu ...

'', better known as Dwarf Jade Plant, which normally uses C₃ fixation but can use CAM if it is drought-stressed, and ''

'', better known as Purslane, which normally uses fixation but is also able to switch to CAM when drought-stressed. CAM has evolved convergently many times. It occurs in 16,000 species (about 7% of plants), belonging to over 300

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencl ...

and around 40

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...

, but this is thought to be a considerable underestimate. The great majority of plants using CAM are

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s (flowering plants) but it is found in

ferns A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except th ...

, Gnetopsida and in

quillwort ''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...

s (relatives of club mosses). Interpretation of the first quillwort genome in 2021 (''I. taiwanensis'') suggested that its use of CAM was another example of convergent evolution. The following list summarizes the taxonomic distribution of plants with CAM:

References

External links

Khan Academy, video lecture
{{DEFAULTSORT:Crassulacean Acid Metabolism Photosynthesis Plant metabolism

Historical background

Overview: a two-part cycle

During the night

During the day

Benefits

Comparison with metabolism

Biochemistry

Use by plants

Aquatic CAM

Ecological and taxonomic distribution of CAM-using plants

See also

References

External links