18. During embryo germination in a grass family an absorptive organ that forms interface between the embryo and the starchy endosperm tissue is called
    (1) Coleorhiza (2) Coleoptile
    (3) Scutellum (4) Mesocotyl

Introduction

In the grass family, seed germination involves a specialized organ called the scutellum, which acts as a critical interface between the embryo and the nutrient-rich starchy endosperm. This thin, shield-like cotyledon plays an essential role in nutrient absorption, supporting early seedling growth before photosynthesis begins.

Structure and Function of the Scutellum

• The scutellum is a thin, highly absorptive cotyledon unique to monocot grasses such as maize, wheat, and rice.​

• It is positioned adjacent to the endosperm and has a large surface area to efficiently absorb sugars, amino acids, and other nutrients degraded from the endosperm starch.​

• Nutrient transport proteins in the scutellum facilitate the movement of reserves into the embryo to sustain germination and seedling establishment.​

• Unlike typical green cotyledons in dicots, the scutellum does not develop into a photosynthetic organ but remains underground during early growth, focusing on nutrient uptake and transfer.​

Germination Process in Grasses

• During germination, enzymes secreted by the scutellum digest starch in the endosperm, liberating nutrients absorbed by the scutellum.​

• These nutrients are then transported to the growing embryonic axis to fuel cell division and elongation.

• The scutellum also acts as a protective interface, managing interactions between the embryo and endosperm while defending against pathogens.​

Clarification of Other Terms

• Coleorhiza (Option 1): A protective sheath covering the embryonic root during germination.

• Coleoptile (Option 2): A protective sheath covering the embryonic shoot, aiding in its emergence through soil.

• Mesocotyl (Option 4): The portion of the embryonic stem between the seed and the coleoptile in monocots, helping position the shoot during germination.

Summary Table: Grass Seed Germination Structures

Conclusion

The scutellum serves as the absorptive organ bridging the developing embryo and starchy endosperm in grasses, making it vital for nutrient uptake and successful seed germination. Hence, the correct answer is (3) Scutellum.