What is the Difference Between Collateral and Bicollateral Vascular Bundles?

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The main difference between collateral and bicollateral vascular bundles lies in the arrangement of xylem and phloem within the bundle. Vascular bundles are structural organizations of vascular tissues (xylem and phloem) found in plants. Here are the key differences between the two types of vascular bundles:

Collateral Vascular Bundles:

  • Contain a single patch of phloem.
  • Xylem is located internal to the phloem (towards the center).
  • Can be open (with a single cambial strip between xylem and phloem) or closed (without cambial strip).
  • Examples: Dicot stem (open) and monocot stem (closed).

Bicollateral Vascular Bundles:

  • Contain two patches of phloem, with xylem in the center.
  • Phloem is located on both sides of the xylem.
  • Always open, containing two cambial strips (one between outer phloem and xylem, and another between inner phloem and xylem).
  • Examples: Cucurbita stem and Cephalandra stem.

In summary, collateral vascular bundles have a single strip of phloem and can be open or closed, while bicollateral vascular bundles have two strips of phloem and are always open.

Comparative Table: Collateral vs Bicollateral Vascular Bundles

The main difference between collateral and bicollateral vascular bundles lies in their arrangement of phloem and xylem tissues. Here is a comparative table highlighting the differences between the two:

Characteristic Collateral Vascular Bundles Bicollateral Vascular Bundles
Definition Collateral bundles have both xylem and phloem on a single axis, with phloem on the outer side of xylem. Bicollateral bundles have xylem between two phloem patches.
Number of Phloem Contains one strip of phloem. Contains two strips of phloem.
Number of Cambium Contains one strip of cambium if open. Contains two strips of cambium, one between outer phloem and xylem, and another between inner phloem and xylem.
Open/Closed Can be open or closed. Always open.
Example Dicot stem. Cucurbita stem.

In summary, collateral vascular bundles have a single patch of phloem on the outer side of xylem, while bicollateral vascular bundles have two patches of phloem on both sides of xylem. Collateral bundles can be open or closed, with a single cambium strip if open, while bicollateral bundles are always open, with two cambium strips.