Question

What is the fate of primary xylem in a dicot root showing extensive secondary growth?

• A. It is retained in the centre of the axis
• B. It gets crushed
• C. May or may not get crushed
• D. It gets surrounded by primary phloem

Answer 1

The correct option is A It is retained in the centre of the axis

In the case of excessive secondary growth, the continuous addition of layers of secondary xylem on the inner side and layers of secondary phloem are produced on the outer side. The primary phloem along with some part of outer secondary phloem gets crushed as new phloem keeps on developing. The primary xylem remains more or less intact and retained in the centre of the axis. However, due to the pressure of the newly formed adjoining tissues, the primary xylem may stop growing.