Question

Name and define different types of vascular bundles.

Answer 1

Hint: Vascular bundle is the arrangement of xylem and phloem strands. To transport water and minerals in the plants, tissue is present which is known as vascular tissue which is found in vascular plants.

Complete step by step answer:
The four main types of vascular bundles: Collateral bundle, Bicollateral bundle, Concentric bundle, Radial bundle.
1. Collateral bundle: It is a type of vascular bundle in which phloem strands are present externally to the xylem strands on the same radius side by side is called a collateral bundle. There are further two types of collateral vascular bundles: closed and open collateral bundle.
a. Closed collateral bundle: Cambium is absent in between phloem and xylem. They do not have normal secondary growth. Example: monocotyledonous stem.
b. Open collateral bundle: Cambium is present in between phloem and xylem. They have secondary growth by the increase in the diameter. Example: dicotyledonous stem.
2. Bicollateral bundle: It is a type of vascular bundle in which phloem situated on the peripheral and inner side of the xylem is called a bicollateral vascular bundle. There are two strips of cambium i.e. inner and outer cambium. Inner cambium is present between inner phloem and xylem. Whereas, outer cambium is present between the peripheral xylem and phloem.
3. Concentric bundle: In this type, one type of the vascular tissue surrounds the other vascular tissue. On the basis of encircling, further divided into two types.
a. Amphivasal bundle: Xylem encircles the central strand of phloem is known as amphivasal bundle. Example: yucca, dracaena.
b. Amphicribral bundle: Phloem encircles the central strand of xylem. Example: selaginella.
Radial vascular bundle: Xylem and phloem strands are separated from each other by non-vascular tissue. They are situated on other axis of radii and are known as radial vascular bundles.

Note:
 Vascular bundle helps in transporting water and minerals through the special tissue known as vascular tissue. There are 4 types of vascular bundles: collateral, bicollateral, concentric and radial vascular bundles.