The correct answer is option 1: Cambium cells. Plant cells generally have nuclei, which are the control centers of the cell. However, cambium cells are an exception to this rule. Cambium cells are responsible for the growth of plants, and they have the unique characteristic of lacking nuclei. This absence of nuclei allows for greater flexibility and efficiency in cell division and growth.

Option 2: Root hairs do have nuclei. Root hairs are specialized extensions of root cells that increase the surface area for absorbing water and minerals from the soil. Like other plant cells, root hair cells contain nuclei.

Option 3: Companion cells are specialized cells found in the phloem tissue of plants, and they are responsible for supporting and assisting the movement of sugars through the plant. Companion cells also have nuclei, as they require genetic information for their functions.

Option 4: Tracheid cells are a type of water-conducting cell found in the xylem tissue of plants. Tracheids cells, like most other plant cells, have nuclei. These nuclei contain the genetic information necessary for the tracheid cells to carry out their water transportation functions.

Therefore, the only plant cells without nuclei among the options listed are cambium cells.