Dr. (Miss) Kalpana R. DatarAssistant Professor

DEPARTMENT OF BOTANYWillingdon College, Sangli.

kalpana_datar@yahoo.com

B.Sc.-I

Types of Vascular Bundles

Vascular Bundle or fascicles-Group of xylem and phloem placed in centre

is called as vascular bundle or fascicles(latin –fascis= bundle).

Functions-a. Conduction and translocation of water and

food.b. Providing mechanical support to the plant

body.

Types of vascular bundles

Three types of vascular bundles-1. Radial – Xylem and phloem patches are separate and present on alternate radii.

2. Collateral and Conjoint -- Xylem and phloem patches are present on same radius and lie side by side.

3.Concentric – One tissue is surrounded by the other.

Vascular Bundle

Radial Conjoint Concentric

Collateral Bicollateral

Open Closed Amphivasal Amphicribal

Xylem & phloem on different radii

Xylem & phloem lie side by side

Xylem & phloem lie side by side on same radius

Cambium present in between xylem &phloem

Cambium absent

Two patches of phloem on either side of xylem

Phloem is surrounded by xylem

xyem is surrounded by phloem

One tissue is surrounded by other

Vascular Bundle

Radial Conjoint Concentric

Collateral Bicollateral

Open Closed Amphivasal Amphicribal

e.g. Root –Sunflower, Maize Root

e.g. Root – Sunflower, Maize Roote.g. Root –Sunflower, Maize Root

e.g. Root – Sunflower, Maize Roote.g. Root- Sunflower

Maize

e. g. DicotStemSunflower Stem

e.g. Monocot StemMaize Stem

e.g. Dracaenastem

e.g. Fern rachis

e.g. Cucurbita stem

Radial Vascular bundles:1.Xylem and phloem patches are on different radii.2.They are in equal number.3.They are alternately arranged.4.This type of vascular bundle is always closed,because

cambium is absent.5.Xylem is Exarch. Protoxylem towards periphery

and metaxylem towards centre.6.Most primitive type of Vascular bundle.7.It is characteristic feature of Roots.8.Depending upon the number of xylem, it may beMonarch-1,Diarch-2,triarch-3,tetrarch-4,pentarch-5,hexarch-6,polyarch-more than 6.e.g. Sunflower root, Maize root.

Phloem

Xylem

Conjoint Vascular bundle1. Xylem and phloem are present on the same radius.

2. They lie side by side on the same radius.

3. There are two types on the basis of phloem patches.a. Collateral- one phloem patch.b. Bicollateral – Two phloem patches.4. Again Conjoint, Collateral vascular bundles are of two

types on the basis of Cambiuma. Open – Cambium present.b. Closed- Cambium absent.

5. Xylem is Endarch.Protoxylem towards pith and

metaxylem towards periphery.

• Xylem and phloem are present on the same radius.

• They lie side by side on the same radius

• Xylem lies on inner side, and phloem on the outer side.

• Xylem is always endarch.• Cambium is present in

between xylem and phloem.• Always open.e. g. Dicot stem- Sunflower

stem

• Xylem and phloem are present on the same radius.

• They lie side by side on the same radius

• Xylem lies on inner side, and phloem on the outer side.

• Xylem is always endarch.• Cambium is absent in

between xylem and phloem.• Always closede. g. Monocot stem- Maize stem

1.Xylem and phloem are present on the same radius.2.Two phloem patches are present on both sides of xylem.3.Cambium strips are present in between xylem and phloem.4.This type of vascular bundle is always open.5. Xylem is endarch.6. The sequence of tissues is inner phloem, inner cambium, xylem, outer cambium and outer phloem.

e.g. Members of Cucurbitaceae, Solanaceae,Myrtaceae, Apocynaceae.

a. Centroxylic or Hadrocentric or Amphicribal

1.Xylem is surrounded by phloem tissues.

2.It is always closed due to absence of cambium.

3.e.g.Fern rachis, Petiolar bundles of flowers and fruits.

Centrophloeic or Leptocentric or Amphivasal

1. Phloem is surrounded by Xylem tissues.

2.It is always closed due to absence of cambium.

3. e.g. Stem of Dracaena, Yucca, Acrous