What does the sheath of a grass plant do?

The sheath of a grass plant serves an essential role in the plant's structure. It wraps around the stem below the leaf, providing protection and support. This characteristic is particularly important as it helps secure the leaf to the stem, allowing it to efficiently capture sunlight for photosynthesis while also protecting the stem from environmental factors. A well-developed sheath can also aid in water retention and contribute to the overall stability of the plant.

In contrast, the other options do not accurately describe the function of the sheath. While flowers may be supported by other parts of the plant, that is not the role of the sheath. The main part of the blade is formed by other components of the grass structure, and the root system's support comes primarily from the roots and lower stem rather than from the sheath itself. Thus, option B best captures the true function of the sheath in a grass plant's anatomy.