Question

Formation of secondary xylem and phloem respectively are

• A. Centrifugal and centripetal
• B. Centripetal and centrifugal
• C. Both centripetal
• D. Both centrifugal

Answer 1

The correct option is B Centripetal and centrifugal

Vascular cambium exhibits two patterns of division; multiplicative divisions or additive divisions, thus, cut more actively at centre. Multiplicative divisions increase the circumference of the vascular cambium. Additive division adds phloem or xylem mother cell that differentiates into their respective cell types.
The primary xylem is in the centre of the stem and thus, secondary xylem is formed towards inner side, while the primary phloem is pushed outward by the new cells that arise from the vascular cambium, i.e., produced towards outer side. Growth pattern that moves towards the centre is called as centripetal while those moving outwards away from centre is called as centrifugal.
Xylem shows centripetal growth while phloem exhibits centrifugal growth pattern.
Thus, the correct answer is option B.