Question

Both a dicot and monocot root possess six vascular bundles. The two can be distinguished by.
A. Presence of lysigenous cavity in monocot root
B. Occurrence of more metaxylem vessels in dicot root
C. Presence of exarch condition in monocot root
D. Outline of vessels

Answer 1

Hint: Dicot root and monocot root are different because monocots tend to have “fibrous roots’’ that are webbed in many directions and these roots occupy upper level of soil as compare with the dicot roots occupy deeper level of soil.

Complete answer:
Dicot root differs from monocot root in the number of xylem strands, the presence of medulla, activity of pericycle and activity of conjunctive tissue. Both kinds of roots have their unique characteristics.

> Option A - Presence of lysigenous cavity in monocot root: Lysigenous cavity is always present in monocot stem or leaf not in monocot root. When protoxylem disintegrates a cavity appears which is known as lysigenous cavity.

> Option B - Occurrence of more metaxylem vessels in dicot root: Primary xylem is of two types metaxylem and protoxylem. Protoxylem is an early formed structure whereas metaxylem is formed late. Primary cell is the same in both monocot and dicot. Thus, metaxylem vessels are found in same number in both dicot and monocot root.

> Option C - Exarch condition is said when there is presence of protoxylem towards periphery and metaxylem is located near the centre area. This search condition is found in both monocot and dicot root whereas the endarch condition is found in stem.

> Option D - Outline of vessels: We can distinguish monocot and dicot roots on the basis of outline form of vessels because the shape of xylem vessels in dicot is angular or polygonal and the shape of vessels in monocot is oval or spherical. Hence, we can distinguish monocot and dicot root on the basis of the outline of vessels.

Hence, the correct answer is option (D).

Note: Other few differences between monocot and dicot roots are:
- The cortex area is narrow in dicot root and wide in monocot root.
- Older dicot roots have a covering of cork whereas older monocot roots show a covering of exodermis.
- Passage cells are absent in dicot and present in monocot.
- The conjunctive tissue is parenchymatous and it forms the cambium and secondary growth is absent in the monocot root.
- Pith is reduced or absent and reduced pith is usually small and at the other hand pith is well developed in monocot roots.