Indigofera

Indigofera is a large genus of over 750 species^[2] of flowering plants belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world.^[2]

Species of Indigofera are mostly shrubs, though some are small trees or herbaceous perennials or annuals. Most have pinnate leaves. Racemes of flowers grow in the leaf axils, in hues of red, but there are a few white- and yellow-flowered species. The fruit is a legume pod of varying size and shape.^[2]

Indigofera is a varied genus that has shown unique characteristics making it an interesting candidate as a potential perennial crop.^{[clarification needed]} 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 update despite varying conditions.

One example of its unique flowering morphology is an open carpel not often seen elsewhere. In addition, it appears that the organ primordial^{[clarification needed]} is often formed at deeper layers than other eudicots.^[3] 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.

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 microcarpa, Indigofera suffruticosa, and Indigofera enneaphylla have shown delayed dehiscence (maturing) of fruits^[4] 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.^[5] Similar to fruit shape, the variation in fruit sizes allows for the thickest and most bountiful fruits to be selected.