Question

Explain the vascular tissue system.

Answer 1

Vascular system consists of xylem and phloem. Elements of xylem and phloem are organised in groups constitute the vascular bundle. Xylem and phloem with cambium is an open vascular bundle and without cambium is called closed vascular bundle. Vascular bundles are broadly divided into three types namely 1. Radial 2. Collateral 3. Concentric types.

1. Radial (Eg-roots): Xylem and phloem lie on different radii on alternate manner

2. Collateral (Eg-stems and leaves): Xylem and phloem lie on the same radius along with vascular bundle together. It is divisible into:

a) Collateral closed: Leaves and monocots no cambium in vascular bundle.

b) Collateral open: Dicots cambium is found in the vascular bundle.

c) Bicollateral open: Cucurbitaceae (sterns) phloem occurs on both the outer and inner sides of xylem due to the presence of two cambial layer.

Concentric vascular bundle: The bundle in which either phloem surrounds the xylem or xylem surrounds the phloem completely.

Types: The concentric vascular bundles are of two types.

a) Amphicribral: The phloem completely surrounds the xylem. E.g. Polypodium.

b) Amphivasal: The xylem completely surrounds the phloem. Eg. Acorus.