Botany lecture notes

Difference between Collateral and Bicollateral Vascular Bundles

Collateral vs Bicollateral vascular bundle

Collateral vs Bicollateral Vascular Bundles
(Similarities and Differences between Collateral and Bicollateral Vascular Bundles)

Vascular bundles are the distinct structural organization vascular tissues (xylem and phloem) and the formation of vascular bundles is one of the advanced characteristics of higher plants. In the stem of seed plants, the vascular tissue (xylem and phloem) occupy together as vascular bundles. However, in roots the xylem and phloem are not associated together and not form the vascular bundles. Such an arrangement of vascular tissue in root is called radial arrangement.

In the previous post we have discussed the Structure and Classification of Vascular Bundles. Based on the relative position and number of phloem strands in vascular bundles, the conjoint vascular bundles are classified into two groups: (1). Collateral vascular bundles and (2) Bicollateral vascular bundles.

Bi-collateral vascular bundles(1). Collateral vascular bundle: A type of conjoint vascular bundle where the xylem occupies inner to a single strand of phloem. Example: dicot stem and monocot stem.

(2). Bicollateral vascular bundles: A type of conjoint vascular bundle where the xylem is situated in the middle of two phloem strands. Example: stem of Cucurbita, Cephalandra (members of Cucurbitaceae Family).

The present post describes the similarities and differences between the collateral and bicollateral vascular bundles in plants with a comparison table.

Similarities between Collateral and Bicollateral Vascular Bundles

Ø  Both are conjoint vascular bundles (xylem and phloem occupy together as bundle).

Ø  Both are present in the stem.

Ø  Both contain only one xylem strand.

Ø  Xylem is endarch in both the groups.

Difference between Collateral and Bicollateral Vascular Bundle

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Botany lecture notes

Anatomy of Dicot Stem: The Primary Structure – Key Points with PPT

Stem Structure Anatomy

Anatomy of Dicot Stem
Anatomy of the Primary Structure of Dicot Stem

“Biology is the study of complicated things that have the appearance of having been designed with a purpose….”
Richard Dawkins

Ø  The anatomy of dicot stem is studied by a T.S. (transverse section) took through the internode of the stem.

Ø  The components of cortex and stele are together known as Ground Tissue.

Ø  Anatomically the dicot stem has the following regions:

(1). Epidermis

(2). Cortex

a).  Hypodermis
b).  Outer cortex
c).   Inner cortex
d).  Endodermis

(3). Stele

a).  Pericycle
b).  Vascular bundles
c).  Medullary rays
d).  Pith

(1). Epidermis

Ø  Epidermis is the outermost layer, composed of parenchymatous cells.

Ø  Usually, epidermis composed of single layer of cells.

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