''Indigofera'' is a large genus of over 750 species of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world.

Description

''Indigofera'' is a varied genus that has shown unique characteristics making it an interesting candidate as a potential perennial crop. Specifically, there is diverse variation among species with a number of unique characteristics. Some examples of this diversity include differences in pericarp thickness, fruit type, and flowering morphology. The unique characteristics it has displayed include potential for mixed smallholder systems with at least one other species and a resilience that allows for constant nitrogen uptake despite varying conditions.

Tree

Species of ''Indigofera'' are mostly shrubs, though some are small trees or herbaceous perennials or annuals. The branches are covered with silky hairs. Most of them have pinnate leaves made of three foliolates with short petioles. Small flowers grow in the leaf axils from long peduncles or spikes, their petals come in hues of red or purple, but there are a few greenish-white and yellow-flowered species. Indigofera flowers have open carpels, their organ primordial is often formed at deeper layers than other eudicots. This variety could have significant implications on its role in an actual perennial polyculture. For example, different flowering morphologies could be artificially selected for in varying directions in order to better fit in different environmental conditions and with different populations of other plants.

Fruit

The fruit is a long, cylindrical legume pod of varying size and shape. The types of fruit produced by different species of ''Indigofera'' can also be divided into broad categories that again show great variation. The three basic types of fruit categories can be separated by their curvature including straight, slightly curved, and falcate (sickle-shaped). In addition, several of the species, including '' Indigofera suffruticosa'' and '' Indigofera microcarpa'', have shown delayed dehiscence (maturing) of fruits. This variation could again allow for artificial selection of the most abundant and nutritious fruit types and shapes. Another way to categorize ''Indigofera'' is by its pericarp thickness. The pericarp (the tissue from the ovary that surrounds the seeds) can be categorized as type I, type II, and type III with type I having the thinnest pericarp and fewest layers of schlerenchymatous (stiff) tissue and type III having the thickest pericarp and most schlerenchymatous layers. Despite the previous examples of delayed dehiscence, most fruits of this genus show normal explosive dehiscence to disperse seeds. Similar to fruit shape, the variation in fruit sizes allows for the thickest and most bountiful fruits to be selected.

Species

, Plants of the World Online accepted over 760 species worldwide. Selected species: *'' Indigofera astragalina'' DC. *'' Indigofera australis'' Willd. *'' Indigofera candicans'' Aiton *'' Indigofera cassioides'' Rottler ex DC. *'' Indigofera cloiselii'' Drake *'' Indigofera cordifolia'' B.Heyne ex Roth *'' Indigofera decora'' Lindl. *'' Indigofera galegoides'' DC. *'' Indigofera georgei'' E.Pritz. *'' Indigofera glaucescens'' Eckl. & Zeyh. *'' Indigofera hendecaphylla'' Jacq. *'' Indigofera heterantha'' Wall. ex Brandis *'' Indigofera hilaris'' Eckl. & Zeyh. *'' Indigofera himalayensis'' Ali *'' Indigofera hirsuta'' L. *'' Indigofera howellii'' Craib & W.W.Sm. *'' Indigofera kirilowii'' Maxim. ex Palibin *'' Indigofera linifolia'' (L.f.) Retz. *'' Indigofera marmorata'' Balf.f. *'' Indigofera miniata'' Ortega *'' Indigofera nephrocarpoides'' J.B.Gillett *'' Indigofera nummulariifolia'' (L.) Livera ex Alston *'' Indigofera pendula'' Franch. *'' Indigofera rothii'' Baker *'' Indigofera sokotrana'' Vierh. *'' Indigofera spicata'' Forssk. *'' Indigofera suffruticosa'' Mill. *'' Indigofera szechuensis'' Craib *'' Indigofera tinctoria'' L. *'' Indigofera tsiangiana'' Metcalf

Ecology

''Indigofera'' species are used as food plants by the larvae of some Lepidoptera species, including the turnip moth (''Agrotis segetum'').

Uses

Indigo dye

Several species, especially '' Indigofera tinctoria'' and '' Indigofera suffruticosa'', are used to produce the dye indigo. Scraps of Indigo-dyed fabric likely dyed with plants from the genus ''Indigofera'' discovered at Huaca Prieta predate Egyptian indigo-dyed fabrics by more than 1,500 years. Colonial planters in the Caribbean grew indigo and transplanted its cultivation when they settled in the colony of South Carolina and

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

where people of the Tuscarora confederacy adopted the dyeing process for head wraps and clothing. Exports of the crop did not expand until the mid-to late 18th century. When Eliza Lucas Pinckney and enslaved Africans successfully cultivated new strains near Charleston it became the second most important

cash crop A cash crop, also called profit crop, is an Agriculture, agricultural crop which is grown to sell for profit. It is typically purchased by parties separate from a farm. The term is used to differentiate a marketed crop from a staple crop ("subsi ...

in the colony (after rice) before the American Revolution. It comprised more than one-third of all exports in value. The chemical aniline, from which many important dyes are derived, was first synthesized from ''Indigofera suffruticosa'' ( syn. ''Indigofera anil'', whence the name aniline). In Indonesia, the Sundanese use ''Indigofera tinctoria'' (known locally as tarum or nila) as dye for batik. Marco Polo was the first to report on the preparation of indigo in India. Indigo was quite often used in European easel painting during the Middle Ages.

References

External links

''Indigofera''.
eFloras Lists. * {{Authority control Fabaceae genera Plant dyes Pantropical flora