testa

Testa is a term used in botany to refer to the seed coat, the protective outer covering of a seed. The word comes from Latin testa, meaning shell or cover.

In seed development, the testa forms from the integuments of the ovule and may include contributions from the ovary and surrounding tissues. It is often composed of several cell layers, including an epidermal layer that is frequently hardened by suberin or lignin.

The primary functions of the testa are to protect the developing seed from mechanical damage and pathogens, regulate water uptake and gas exchange, and influence dormancy and germination. It may contain pigments and other compounds that deter predators and contribute to seed longevity.

Variation in testa structure and composition is common among plant species. Some seeds have a hard, impermeable testa that enforces physical dormancy and requires scarification to germinate, while others have a thin or permeable testa that allows quicker water uptake. Testa color, texture, and chemical makeup also vary and can affect interactions with the environment and predators.

Ecologically and agriculturally, testa traits influence seed dispersal, timing of germination, and storability. Plant breeders may select for specific testa characteristics to improve seed durability, germination performance, or resistance to pathogens.

See also: seed coat, integument, dormancy.