In the wheat grain, the embryo contains a single large cotyledon that has a shield-like shape. This cotyledon is referred to as :

scutellum

The correct answer is option (2) - scutellum

The scutellum is a specialized structure found in the embryo of grasses, including wheat. It is a single, large, shield-shaped cotyledon that is responsible for nutrient absorption during germination. It is located between the embryonic axis and the endosperm of the grain. The scutellum plays a vital role in providing nutrients to the developing seedling until it can establish its own photosynthetic capabilities. Therefore, in the given context, the large, shield-shaped cotyledon in the wheat grain is known as the scutellum.

At the lower end of the embryonal axis, there is a structure called the coleorrhiza, which encloses the radicle (root tip) and the root cap. The coleorrhiza is an undifferentiated sheath.

Above the point where the scutellum is attached, the embryonal axis continues as the epicotyl. The epicotyl contains a shoot apex and a few leaf primordia. Enclosing these structures is a hollow foliar structure known as the coleoptile.