Cotton seeds are the reproductive units of the cotton plant. Beyond propagation, these seeds hold significant economic value. They are processed for cottonseed oil, used in food and cosmetics, and the remaining meal serves as protein-rich livestock feed.
Outer Appearance
When cotton is harvested, seeds are encased within a fluffy mass of fibers known as lint. This lint gives the structure a soft, somewhat irregular, and often off-white or brownish appearance. The fibers, which can be 1 to 2 inches long, originate from the seed coat’s epidermal cells and create a fuzzy texture. While the underlying seed is ovoid and somewhat pointed, the surrounding lint makes the package appear less defined, often resembling a small, irregular tuft.
The dimensions of a cotton seed, including its lint, vary, but the diameter ranges from 5.05 to 6.57 millimeters. This fibrous covering aids natural seed dispersal and makes cotton a valuable textile crop. Some varieties have naturally colored lint, such as green or shades of brown.
The True Seed Beneath the Lint
Once lint is removed through ginning or delinting, the cotton seed’s appearance is revealed. The delinted seed is ovoid, meaning it has an egg-like or somewhat pointed shape. Its surface can range from smooth to slightly ridged, depending on the variety.
The delinted cotton seed is dark brown to black. This contrasts with the lighter lint. Delinting reveals the more defined, somewhat angular or teardrop shape of the seed, which is roughly 60% cotyledon by weight.
Internal Components
Internally, the cotton seed is composed of an embryo encased within a protective seed coat. This seed coat, or testa, safeguards the delicate structures within. The embryo comprises several distinct parts important for the plant’s future growth.
Two prominent structures within the embryo are the cotyledons, often called seed leaves. These large, folded cotyledons constitute a significant portion of the seed’s weight and serve as primary storage sites for nutrients like proteins, oils, and starch, which fuel initial germination and seedling development. The embryo also contains a small embryonic root, known as the radicle, which is the first part to emerge from the seed during germination to anchor the plant and absorb water. Additionally, a rudimentary embryonic shoot, or plumule, will develop into the stem and leaves above ground.