Question

you are given a fairly old piece of dicot stem and a dicot root. Which of the following anatomical structures will you use to distinguish between the two ?
1. cortical cells
2. secondary xylem
3. secondary phloem
4. protoxylem
( AIPMT 2014)

Answer 1

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).