Question

Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by

• A. absence of secondary phloem
• B. presence of cortex
• C. position of protoxylem
• D. absence of secondary xylem

Answer 1

The Correct Option is C

In dicot root the protoxylem is located near the periphery of the vascular cylinder, the metaxylem farther inward. In roots xylem is exarch or centripetal. In dicot stem the protoxylem is located near the centre of vascular bundle and metaxylem is located near the periphery i.e. the xylem is endarch or centrifugal.

Answer 2

The protoxylem is placed towards the perimeter of the vascular cylinder, away from the center (exarch condition), while the metaxylem is located in the middle. The protoxylem in the dicotyledonous stem is placed near the middle of the vascular bundle (endarch condition), whereas the metaxylem is located further from the centre. As a result, the location of the protoxylem distinguishes an anatomically rather ancient dicotyledonous root from a dicotyledonous stem.