Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by:
Correct answer: C. Position of protoxylem
- A. Absence of secondary phloem
- B. Presence of cortex
- C. Position of protoxylem
- D. Absence of secondary xylem
Explanation
Procambium, which is a meristematic tissue, gives rise to the primary xylem and phloem. In the case of primary xylem, there are two types of xylems that are formed - protoxylem and metaxylem. The protoxylem is the first formed primary xylem. Metaxylem is the primary xylem that is formed after the protoxylem. The protoxylem and metaxylem are arranged in two different ways in the stem and roots. In the stem, the protoxylem is placed towards the center. This is known as an endarch condition. In roots, the protoxylem is arranged towards the periphery. This is known as the exarch condition. Hence, a fairly old dicotyledonous root is distinguished from a dicotyledonous stem by the position of the protoxylem.
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