Question

Secondary growth in dicots and gymnosperms occurs by

• A. Formation of vascular rays
• B. Thickening of tracheary elements
• C. Formation of meristematic cells in vascular region
• D. Development of meristematic cells in vascular and cortical regions

Answer 1

The correct option is D Development of meristematic cells in vascular and cortical regions

Intrafascicular cambium (present between xylem and phloem) and interfascicular cambium together form a complete cambium ring, called as vascular cambium or just cambium. Vascular cambium exhibits two patterns of division i.e., multiplicative divisions and additive divisions. Additive division adds phloem/xylem mother cell that differentiates into their respective cell types thereby causing stellar growth. The cells that cut off towards centre produce secondary xylem thereby causing thickening of tracheary elements and those that cut off to the outside are converted into secondary phloem tissues.