Chapter 7, Problem 1RQ

Summary Introduction

To write:

Why do leaves have no secondary xylem and phloem?

Introduction:

Secondary xylem signifies towards the formation, which takes place post the vascular cambium's secondary growth. This kind of xylem is not found in non-woody plants, however, is generally witnessed in trees and shrubs. The secondary phloem refers to the food-conducting tissue, and at certain occasions is considered as the inner bark of the tree. The vascular cambium gives rise to secondary xylem within the ring and secondary phloem on the external, thus, pushing the primary phloem and xylem away.

Explanation of Solution

Secondary phloem and xylem are produced at the time of the secondary growth from vascular cambium in the stem and roots. The leaves do not exhibit secondary xylem and phloem as they endure for a brief duration. The secondary phloem and xylem perform a big structural activity in trees, while the leaves do not require the support.

The secondary phloem and xylem need a good concentration of energy, thus, if leaves possess secondary phloem and xylem, then there would be an ample amount of energy waste.

Conclusion

The leaves do not exhibit secondary phloem and xylem as the leaves last for a small time duration, and an ample amount of energy would get lost, if the leaves exhibit secondary xylem and phloem as good amount of energy is needed for their proper function.