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I need help with Anatomatically fairly old discotyledonous root is distinguished from the dicotyledonous stem by

Anatomatically fairly old discotyledonous root is distinguished from the dicotyledonous stem by

  • Option 1)

    absence of secondary phloem

  • Option 2)

    presence of cortex

  • Option 3)

    postion of protoxylem

  • Option 4)

    absence of secondary xylem

 
Answers (1)
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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 

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