Question

With the help of suitable examples describe the various types of vascular bundles in plants.

Answer 1

A group of xylem and phloem forms the vascular bundles. The different types of vascular bundles are

• Radial bundles(simple)

Xylem and phloem occupy different radii on the axis separated by non-conductive tissues. Examples: dicot and monocot roots.

• Concentric:

One vascular element surrounds the other on all the sides. It is of two types.

a) Amphivasal or Leptocentric:

Xylem is seen outside that surrounds the phloem. Ex: Dracaena, yucca.

b) Amphicribal or Hydrocentric:

Phloem is seen towards the outer side and xylem towards the inner side. Ex: Hydrilla, Pteris.

• Conjoint:

Xylem and phloem on same radii.

a) Collateral:

Xylem and phloem arranged side by side on the same radius. This may be open or closed. Xylem is seen towards the inner side and phloem in the outer side.

a 1) Collateral open:

Cambium is present in between the xylem and phloem. Ex: Dicot stem.

a 2) Collateral closed:

Cambium is no present in between the xylem and phloem. Ex: Monocot stem.

b) By collateral:

Two patches of cambium and one patch of xylem at the middle. Ex: Cucurbitaceae, Solanaceae.