Question

with the help of suitable example describe the various types of vascular bundles in plant​

Answer 1

Answer:

The following points highlight the four main types of vascular bundle. The types are: 1. Collateral Bundle 2. Bicollateral Bundle 3. Concentric Bundle 4. Radial Vascular Bundle.

Types of Vascular Bundle in T.S.

Different Types of Vascular Bundles

Type # 1. Collateral Bundle:

A vascular bundle in which a strand c f phloem is present external to the strand of xylem on the same radius side by side is known as collateral bundle.

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Cambium may be present or absent in between xylem and phloem, and so there are the following two types of collateral bundle:

(a) Closed collateral bundle:

In this type cambium is absent in between xylem and phloem. Therefore stems having this type of bundle do not have normal secondary growth. Ex. Monocotyledonous stem. Usually these bundles are enclosed within bundle sheath made up of sclerenchyma and those that lack the sheath are considered as anomalous (e.g. Asparagus stem).

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(b) Open collateral bundle:

An open collateral vascular bundle has cambium called fascicular cambium between xylem and phloem. The bundles can increase in diameter by normal secondary growth with the help of fascicular cambium. Ex. Dicotyledonous stem.

Type # 2. Bicollateral Bundle:

A vascular bundle with phloem situated on the peripheral and inner side of xylem is known as bicollateral bundle. A strip of cambium termed outer cambium is present between the peripheral phloem and xylem; another strip of cambium, termed inner cambium, is also present between inner phloem and xylem.

The peripheral or external phloem is termed as outer phloem whereas the inner or internal phloem is called inner phloem. The sequence of vascular tissues in the bicollateral bundles from periphery toward centre is outer phloem, outer cambium, xylem, inner cambium and inner phloem.

These bundles are open type as strips of cambia are present but the secondary thickening occurs only by the outer cambium, i.e. cambium present between the outer phloem and xylem. Ex. Cucurbita stem.