testae

Testae is the plural form of testa, a botanical term referring to the seed coat of a seed-bearing plant. The seed coat develops from the integuments of the ovule as the seed matures and surrounds the embryonic plant and stored nutrients. Testae can comprise multiple layers, commonly including an outer epidermis and inner supportive tissue such as sclerenchyma, and may be hardened or lignified. They frequently determine the texture, color, and surface pattern of seeds.

Functions of the testae include protecting the embryo from mechanical damage, pathogens, and desiccation. They also help regulate water uptake and gas exchange and can contribute to seed dormancy by forming a water-impermeable barrier in some species. Some seeds feature specialized coatings or compounds that deter herbivory or assist in dispersal by interacting with animals or the environment.

Variation in testa morphology is common across plant taxa. Thickness, permeability, and surface sculpture (for example smooth, reticulate, or pitted textures) can be useful characters in seed identification and taxonomy. In some groups, the testa fuses with other surrounding structures, such as the pericarp, influencing how seeds are released and dispersed.

Etymology: testa is Latin for "shell." The plural testae is used in botanical contexts to describe the coats of multiple seeds. See also: seed coat, tegmen, pericarp.