Long Answer
Medium difficulty • Structured explanation
Question 1
Long FormCompare and contrast the internal anatomy of a dicotyledonous root and a monocotyledonous root, highlighting at least five structural differences.
- Both dicot and monocot roots share a basic plan: epiblema (epidermis with root hairs), cortex, endodermis with Casparian strips, pericycle, vascular bundles, and pith — establishing the common ground for comparison.
- The number of xylem bundles is a key distinguishing feature: dicot roots typically have two to four xylem bundles (oligarch), while monocot roots are polyarch with more than six xylem bundles arranged radially.
- Pith size differs markedly — in dicot roots the pith is small or inconspicuous due to the extensive central vascular tissue, whereas in monocot roots the pith is large and well developed, occupying a prominent central area.
- Secondary growth is a significant difference: dicot roots undergo secondary growth through the activity of a cambium ring formed from conjunctive tissue and pericycle, increasing girth over time. Monocotyledonous roots do not undergo any secondary growth.
- In dicot roots, a cambium ring develops later between xylem and phloem; this cambium is absent in monocot roots, which permanently retain their primary structure without any lateral meristem activity.
- The conjunctive tissue (parenchyma between xylem and phloem) contributes to cambium formation in dicots but remains purely structural in monocots; additionally, the polyarch condition of monocot roots leaves less room for a discrete central pith compared to the oligarch dicot root.