Page 1 - Lesson Notes
P. 1
SAI International School
Subject- Biology, Class- IX
Chapter- Tissues
Subtopic- Complex Permanent Tissue
Module- 11
Lesson Notes
(B) COMPLEX PERMANENT TISSUES
o The complex tissue consists of more than one type of cell having a common
origin. All these cells coordinate to perform a common function.
o Complex tissues are of two types: Xylem or wood and phloem or bast.
o Xylem and phloem are both conducting tissues and also known as vascular
tissues; together both them constitute vascular bundles.
(i) Xylem:
o Xylem is a vascular and mechanical
tissue.
o Xylem is composed of cells of four
different types:
a. Tracheids- These are long
elongated cells with tapered
ending. The cells are dead. It
transports water through pits.
b. Vessels - It is a pipe like
structure, dead and has lignified
thick cell wall.
c. Xylem parenchyma – These are living cells. They store food and nutrients.
d. Xylem sclerenchyma (or fibres) - These are dead cells. They provide
mechanical support to plant.
o Except xylem parenchyma, all other elements are dead and bounded by thick
lignified wall.
o Tracheid and vessels are tubular structures.
Functions:
o Carry water and mineral salts upward from the root to different parts of
shoots, hence also called water conducting tissue.
o Walls of tracheid, vessels and sclerenchyma of xylem are lignified; they give
mechanical strength to the plant body.
o The parenchyma stores food and helps in the sideway conduction of water.
