Tissues in Action | Class 9 Science Notes

3.2.4 Permanent tissues

Permanent tissues are groups of cells that have lost the ability to divide and have become specialized for specific functions such as protection, support, and conduction. They are formed by differentiation of meristematic cells. Permanent tissues are classified into simple and complex types. Simple permanent tissues consist of only one type of cell and include parenchyma, collenchyma, and sclerenchyma. Parenchyma cells are living with thin walls and intercellular spaces; they store food and perform photosynthesis. Collenchyma cells have unevenly thickened walls providing flexible support, allowing bending without breaking. Sclerenchyma cells have thick, lignified walls, are mostly dead, and provide hardness and strength, found in stems, leaf veins, and seed coats. Complex permanent tissues consist of more than one cell type and include xylem and phloem, which conduct water, minerals, and food throughout the plant. Xylem contains tracheids, vessels, xylem parenchyma, and fibers; phloem contains sieve tubes, companion cells, phloem parenchyma, and fibers. These tissues work together to support plant structure and transport vital substances.

📊 Diagram: See figure_10: Internal structure of a sunflower stem; figure_11: (a) Parenchyma; figure_12: (b) Collenchyma; figure_13: (c) Sclerenchyma; figure_14: Vascular tissue: (a) xylem; figure_15: Vascular tissue: (b) phloem; figure_16: Tissue systems in plants

🔗 Connection: Leads to study of animal tissues and their types.