Aleurone Layer is the outermost proteinaceous layer of endosperm.

• A. Endosperm
• B. Tegmen
• C. Testa
• D. Aleurone Layer

Answer: (D)

The key idea here is identifying the specific boundary layer that surrounds the starchy endosperm in cereal seeds. The aleurone layer is the outermost layer of the endosperm, composed of one or a few cells thick and rich in proteins and lipids. Its main role is to respond during germination by producing and releasing enzymes like proteases and amylases to mobilize the stored nutrients in the endosperm for the growing seedling. This makes it distinct from the endosperm tissue itself (which stores starch), and from the seed coat structures like the testa or tegmen, which are outside the endosperm. Therefore, the statement matches the aleurone layer, the outermost proteinaceous boundary of the endosperm.