In monocots, grafting is not possible as

The correct option is they lack cambium.

Grafting is a widely used horticultural technique where the tissues of two different plants—the scion (the upper part containing the desired buds) and the stock (the rooted lower part)—are joined together so that they continue to grow as a single plant. For grafting to be successful, the vascular cambium of both the scion and the stock must align and come into close contact.

The vascular cambium is a layer of active, meristematic cells responsible for secondary growth in plants. When a graft is made, the cambium cells divide rapidly to produce a mass of cells known as a callus. This callus heals the wound and differentiates into new vascular tissues (xylem and phloem), establishing a continuous connection that allows water, nutrients, and food to flow between the stock and scion.

Monocotyledonous plants (monocots) have closed vascular bundles that are scattered throughout the ground tissue of the stem. Unlike dicotyledonous plants (dicots), monocots do not have a lateral meristem or vascular cambium between the xylem and phloem. Because they lack cambium, they cannot produce the new vascular tissues required to fuse the scion and stock together. As a result, the graft union cannot heal, making grafting impossible in monocots.