Anatomatically fairly old discotyledonous root is distinguished from the dicotyledonous stem by
absence of secondary phloem
presence of cortex
postion of protoxylem
absence of secondary xylem
Centrifugal or Endarch Development -
Protoxylem is formed near the central axis and metaxylem is formed away from centre (towards periphery).
- wherein
Example stem of angiosperm and gymnosperm.
Centripetal or Exarch -
Protoxylem formed away from the central (periphery) and metaxylem towards the centre.
- wherein
Example: Roots
Whenever we want to distinguish between stem and root, we should look for position of protoxylem. In roots, the position of protoxylem is exarch (protoxylem towards periphery, metaxylem towards center) while in stem it is endarch (protoxylem towards center and metaxylem towards periphery).
Option 1)
absence of secondary phloem
This solution is incorrect
Option 2)
presence of cortex
This solution is incorrect
Option 3)
postion of protoxylem
This solution is correct
Option 4)
absence of secondary xylem
This solution is incorrect