Question

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

• A. Position of protoxylem
• B. Absence of secondary xylem
• C. Absence of secondary phloem
• D. Presence of cortex

Answer 1

The correct option is A Position of protoxylem

Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by position of protoxylem
In dicot roots, the protoxylem lies towards periphery of the vascular cylinderand metaxylem lies towards the centre. Such arrangement of primary xylem is called exarch.
In dicot stems, the protoxylem lies towards the centre (pith) and the metaxylem lies towards the periphery of the organ. This type of primary xylem is called endarch.