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CBSE - IX
Plant Tissues
Plant Tissues
A group of cells, that are similar in structure and work together to achieve a particular function, forms a tissue. Types of plant tissues include meristematic and permanent tissues.Meristematic tissues are rapidly dividing tissues.Apical meristem is present at the apical or growing tips of stems and roots. Lateral meristem is present in the radial portion of the stem or root. Intercalary meristem occurs at the base of the leaves or at the internodes. Old meristematic cells lose the capacity to divide and transform into permanent tissues.Types of permanent tissues include parenchyma, collenchyma and sclerenchyma.Parenchyma containing chloroplasts are called chlorenchyma. Parenchyma containing large air cavities are called aerenchyma.Complex permanent tissues are made of more than one type of cells and are of
2 types-xylem and phloem.Tracheids are tubular dead cells that transport water.Vessels are elongated dead cells that transport water and minerals.Xylem parenchyma cells are living and they store food.Xylem fibres are elongated dead cells with lignin that provide mechanical support.Sieve tubes are elongated living cells that transport food from leaves to the stem and the roots.Companion cells help in conduction of food to sieve tubes.Phloem parenchyma store food.Phloem fibre provide mechanical support.Protective tissue protects the plants from the surroundings.Epidermis is the outermost protective layer of roots, stems and leaves. Outermost layer in older roots and stems is called cork that contain dead cells. Epidermis is covered with a water proof layer called cuticle.
