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A tissue is a group of cells having a common origin and usually performing common functions. All the plant organs like roots, stems, leaves, flowers and fruits are made up of different kinds of tissues to perform different functions. Plant tissues are classified into two main groups –
- Meristematic tissues
- Permanent tissues
Permanent Tissues
Permanent Tissues are made of mature cells that have undergone growth and differentiation. Permanent tissues originate from meristematic tissues and occupy a fixed position in the plant body. These cells possess definite shape, size and function. Though permanent tissues have lost their power of division under special circumstances, they may resume power of division.
Permanent Tissues Classification
Depending upon their origin, permanent tissues are of three types – 1. Simple Permanent Tissues, 2. Complex Permanent Tissue, 3. Special Permanent Tissues.
1. Simple Permanent Tissue
Simple permanent tissue is homogenous tissue and made up of single cell types through the origin, structure and function are the same. They have been divided into three types-
Parenchyma | Collenchyma | Sclerenchyma |
• The cell looks like an oval or spherical shape. • Hemicellulose or cellulose are the main part of the cell wall. • The cell has a thin wall. • The cell consists of vacuoles and a tiny nucleus. • It can be seen in every part of the plant. • Dense and living protoplasm. |
• The cells are tall and thick-walled. • Cellulose and pectin are there in the formation of cell walls. • As pectin is present in the cell wall it has the highest refractive index. • It is seen in the epidermis and the vascular bundle of the dicot leaf. • Chloroplast is limited in the cells as compared to others. • The cells possess no intercellular spaces. |
• These are lifeless tissues, relatively hard and rigorous in texture. • Cells are thick-walled with numerous sizes and patterns. • These furnish mechanical backing and rigidity to the plant. |
2. Complex Permanent Tissue
The complex permanent tissues are made of several varieties of cells achieving different functions. They are of two types:
Xylem | Phloem |
• It transfers water and nutritive sustenance from the roots to the leaves of the plant. • It delivers support to the plants. • It is distributed into the tracheid, vessels, xylem fibre, and xylem parenchyma. | • It translocates the ready organic nutrition from the leaves to different portions of the plant. • It is commonly known as bast. • It is formulated of sieve tubes, companion cells, phloem parenchyma, and phloem fibres. |
3. Special Permanent Tissues
are adapted structurally to perform purposes secretory in nature. They are of two types:
Laticiferous Tissues | Glandular Tissues |
• The plant tissues possess latex. • They derive from the meristematic tissues and evolve with other tissues. • The cells are expanded, thin-walled and multi-nucleated. • Examined in a substantial number of families such as Euphorbiaceae, Apocynaceae, and Composite. | • They acquire various glands that conceal oil, resins, tannin, and mucilage. • The gland is positioned on the epidermis. |
Conclusion
Tissues are a group of cells which are having a common origin and usually perform common functions. Plants, as well as animals both, are made up of cells. In plants particularly, the parts of it for example roots, stems, leaves, flowers and fruits are made up of different kinds of tissues that perform different functions in them. Plant tissues can be diversified into two main groups which are meristematic tissue and permanent tissue. Permanent tissue is made up of cells which undergone growth and differentiation. Though they lost their power of division under special circumstances, they may resume power of division. Depending on their origin, permanent tissues can be classified into three types which are simple permanent tissues, complex permanent tissues and special permanent tissues.
