Answer:
Permanent tissues are derived from
meristematic tissue but their cells have lost the power of division and have
attained their definite forms.
Permanent tissues are classified into the
following two types:
(i) Simple permanent tissue
(ii) Complex permanent tissue
(i) Simple permanent tissues:
These tissues are composed of cells which are structurally and functionally
similar. Simple permanent tissues are further classified into the following
three types:
(a) Parenchyma: Parenchyma
forms the bulk of the plant body.
Parenchyma cells are living and
possess the power of division.
(b) Collenchyma:
Collenchyma tissue is also living. It is characterized by the deposition of
extra cellulose at the corners of the cells.
(c) Sclerenchyma:
Sclerenchyma cells are dead cells and they are devoid of protoplasm. The cell
walls of Sclerenchyma are largely thickened with deposition of lignin.
Complex permanent tissues:
The complex tissues consist of more the one type of cells having a common origin.
All these cells coordinate to perform a common function.
Complex tissues are of the
following two types:
(a) Xylem: Xylem is a
vascular and mechanical tissue. It is conducting tissue. Xylem is composed of
four different types of cells: (i) Tracheids (ii) Vessels (iii) Xylem
parenchyma (iv) Xylem Sclerenchyma.
Except xylem parenchyma, all
other xylem elements are dead an bounded by thick lignified walls.
(b) Phloem: Like xylem,
phloem is vascular but has no mechanic function. Phloem is composed of following
four elements: (i) Sieve tubes (ii) Companion cells (Hi) Phloem parenchyma (iv)
Phloem fibres.
Except phloem fibres, all other
phloem elements are living.
Xylem and phloem are both
conducting tissues and also known as vascular tissues; together, both of them
constitute vascular bundle.
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