Write a note on vascular tissue system.

Explanation

(i) It consists of xylem and phloem tissues.
(ii) They are present in the form of bundles called vascular bundles .
(iii) Xylem conducts water and minerals to different parts of the plant.
(iv) Phloem conducts food materials to different parts of the plant.
There are three different types of vascular bundles namely :
(i) Radial (ii) Conjoint
(iii) Concentric
(i) Radial Bundles:
Xylem and phloem are present in different radii alternating with each other. Eg: roots.
(ii) C onjoint bundle s : Xylem and phloem lie on the same radius. There are two types of conjoint bundles.
a) Collateral :
(i) Xylem lies towards the cent re and phloem hes towards the periphery.
(ii) When cambium is present in collat eral bundles , it is called open. Eg: dicot stem and collateral bundle without cambium is called closed.
Eg: monocot stem.
b) Bicollateral :
In this type ofbundle, the phloem is present on both outer and inner side of xylem.
Eg: cucurbita.
(iii) Concentric bundles : Vascular bundle in which xylem completely surrounds the phloem or viceversa is called concentric vascular bundle. It is of two types:
1. Amphivalsal : Xylem surrounds phloem. Eg: Dracaena
2. Amphicribral : Phloem surrounds xylem. Eg: Ferns
Endarch : Protoxylem lies towards the centre and metaxylem lies towards the periphery. Eg: stem.
Exarch : Protoxylem lies towards the periphery and metaxylem lies towards the centre Eg: roots .