4-Chloroindole-3-acetic acid (4-Cl-IAA) is an organic compound that functions as a

plant hormone Plant hormone (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, from embryogenesis, the regulation of organ size, pa ...

Synopsis

It is a member of the class of compounds known as

auxin Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...

s and a chlorinated analogue of the more common

indole-3-acetic acid Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists. IAA is a derivative of indole, co ...

(IAA) auxin. 4-Cl-IAA is found in the seeds of a variety of plants, particularly

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...

s such as peas and broad beans. In one study it is written that the substance is "mainly found in reproductive structures" and "is thought to be restricted to members of the leguminous tribe ''

Fabeae The tribe Fabeae (sometimes referred to as "Vicieae") is one of the subdivisions of the plant family Fabaceae. It is included within the Inverted repeat-lacking clade (IRLC). Five genera are included: * ''Lathyrus'' L. (vetchlings) * ''Lens'' Mil ...

'', specifically "the genera ''

Vicia ''Vicia'' is a genus of over 240 species of flowering plants that are part of the legume family (Fabaceae), and which are commonly known as vetches. Member species are native to Europe, North America, South America, Asia and Africa. Some other ...

'', ''

Pisum ''Pisum'' is a genus of flowering plants in the family Fabaceae, native to southwest Asia and northeast Africa. It contains one to five species, depending on taxonomic interpretation; the International Legume Database (ILDIS) accepts three speci ...

'', ''

Lathyrus ''Lathyrus'' is a genus of flowering plants in the legume family Fabaceae, and contains approximately 160 species. Commonly known as peavines or vetchlings, they are native to temperate areas, with a breakdown of 52 species in Europe, 30 species ...

'', ''

Lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

'', and ''

Vavilovia ''Vavilovia formosa'' is a species of flowering plants in the legume family, Fabaceae. It belongs to the subfamily Faboideae. It is the only member of the genus ''Vavilovia''. It was named after the Russian geneticist, economic botanist, and plan ...

''". In

Pisum sativum The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...

, 4-Cl-IAA biosynthesis diverges from IAA biosynthesis when the amino acid

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α- carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...

is chlorinated to form 4-chlorotryptophan (4-Cl-Trp); the biosynthesis of 4-Cl-IAA then precedes parallel to that of IAA. Engvild hypothesized in 1996 that 4-Cl-IAA may be a "death hormone" that maturing seeds use to trigger death of the parent plant by mobilizing nutrients to be stored in the seed. Lam et al found the substance in the seeds of ''

Medicago truncatula ''Medicago truncatula'', the barrelclover, strong-spined medick, barrel medic, or barrel medick, is a small annual legume native to the Mediterranean region that is used in genomic research. It is a low-growing, clover-like plant tall with trifol ...

'', ''

Melilotus indicus ''Melilotus indicus'', sometimes incorrectly written ''Melilotus indica'', is a yellow-flowered herb native to northern Africa, Europe and Asia, but naturalized throughout the rest of the world. Common names in English include sweet clover (or s ...

'', and three species of ''

Trifolium Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The genus h ...

''.

References

Auxins Indoles Chloroarenes Halogen-containing natural products Acetic acids {{heterocyclic-stub