Permanent tissue are derived from meristematic tissue but their cells have lost power of division and have attained their definite forms.
Permanent tissue are classified into the following two types:
(i) Simple permanent tissue
(ii) Complex permanent tissue
(i) Simple Permanent tissue: These tissues are composed of cells which are structurally and functionally similar. Simple permanent tissue 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 are dead cells and they are devoid of protoplasm. The cell walls of Sclerenchyma are largely thickened with deposition of lignin.
(ii) Complex permanent tissues: The complex tissue consist of more than one type of cells having a common origin. All these cells coordinate to perform a common function. Complex tissue are of the following two types:
(a) Xylem: Xylem is a vascular and mechanical tissue. It is a 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 and bounded by thick lignified walls.
(b) Phloem: Like xylem, phloem is also vascular but has no mechanical function. Phloem is composed of following four element s: (i) Sieve tubes (ii) Companion cells (iii) Phloem parenchyma (iv) Phloem fibers.
Except phloem fibers, all other phloem elements are living.
Xylem and phloem are both conducting tissues and are also known as vascular tissues. Together, both of them constitute vascular bundle.
