Which type of plant has a hollow, jointed stem known as a culm?

The correct answer is grass. Grasses are characterized by their hollow, jointed stems called culms, which distinguish them from other types of plants. The culm provides structural support and enables the plant to grow tall, facilitating access to sunlight, which is crucial for photosynthesis. This hollow structure also helps in the plant's flexibility and resistance to lodging, where the stems bend or break under their own weight or due to environmental factors.

In contrast, sedges and rushes typically do not possess hollow stems, as they have different morphological characteristics. Forbs, on the other hand, are primarily broadleaf herbaceous plants that do not share the same stem structure as grasses. Understanding the unique features of grasses, including the culm, is essential in agronomy for identifying plant types and understanding their ecological roles.