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How do plant ovule integuments become a seed coat?

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A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

In plant biology, the seed coat—also known as the testa—is derived directly from the one or two protective integuments that surround the ovule.123

As the ovule matures into a seed following fertilization, these integuments undergo developmental changes to form a protective outer layer. This transformation often results in a structure that becomes hard and stony, providing essential protection for the developing embryo and its nutritive tissue.12

Depending on the plant species, the resulting seed coat may exhibit various characteristics:
* Texture and Composition: It may become hard, stony, smooth, or glassy, and can sometimes feature a waxy covering.24
* Specialized Structures: The coat may be ornamented with prickles, sclerified hairs, or wings. In some cases, it may consist of an outer fleshy, brightly colored layer (sarcotesta) and an inner stony layer (sclerotesta).2
* Functional Role: The mature seed coat plays a critical role in seed dormancy by mechanically restricting embryo expansion, blocking water uptake, or impeding gas exchange.4