The number of xylem groups in a dicot root such as bean is described as:

1. In the dicot root the vascular bundle is radial and the xylem is exarch. 2. The number of xylem groups in the dicot root is fixed and limited. 3. The dicot root is described as tetrarch, having four xylem groups. 4. So tetrarch is the correct answer. 5. Option A polyarch means many groups and describes the monocot root, the trap. 6. Option C diarch (two) does not match the dicot root described here. 7. Option D monarch (one) is also incorrect for the dicot root. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 12 Plant Anatomy and Plant Physiology "Differences between Dicot and Monocot root", p.184_