Xylem & Phloem Distribution (Cambridge International AS Biology)

Spec point — 7.1.2 · describe the distribution of xylem and phloem in transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants

Xylem & phloem distribution

Xylem

• The functions of xylem tissue in a plant are:

  • Vascular tissue that carries dissolved minerals and water up the plant
  • Structural support

• Xylem tissue is found, along with phloem tissue and other tissues, in vascular bundles

Phloem

• The location of the vascular bundles is dependent on which organ they are in, as the different organs are under different stresses:

  • In the roots the vascular bundle is found in the centre

    • On the edges of the centre core is the phloem tissue

  • In the stems, the vascular bundles are located around the outside

    • The phloem tissue is found on the outside (closest to the epidermis)

  • In the leaves, the vascular bundles form the midrib and a branching network of veins

    • The phloem tissue is found on the lower side of the bundles (closest to the lower epidermis)

The distribution of xylem and phloem tissue in the roots, stem and leaves in a herbaceous dicotyledonous plant

Exam Hint In roots and stem, the xylem tissue is found on the inside.

However, in leaves, xylem is found above phloem tissue.