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  • Biology – Tissues – Notes For W.B.C.S Examination.
    Posted on January 27th, 2019 in General Science
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    Biology – Tissues – Notes For W.B.C.S Examination.

    জীববিজ্ঞান – টিস্যু – WBCS পরীক্ষার জন্য নোট।

    • A group of cells that are similar in structure and work together to accomplish a particular function is known as tissue.Continue Reading Biology – Tissues – Notes For W.B.C.S Examination.
    • Tissues are categorized as −
      • Plant Tissue &
      • Animal Tissue
    • Let’s discuss them in brief −

    Plant Tissue

    • Following are the major types of plant tissue −
      • Meristematic Tissues
      • Permanent Tissues
        • Simple Permanent Tissues
          • Parenchyma
          • Collenchyma
          • Sclerenchyma
          • Epidermis
        • Complex Permanent Tissue
          • Xylem
          • Phloem

    Meristematic Tissue

    • Meristematic tissue mainly consists of actively dividing cells, and helps in increasing the length and thickening the stems of the plant.
    • Meristematic tissue, commonly, present in the primary growth regions of a plant, for example, in the tips of stems or roots.
    • Depending on the region (where the meristematic tissues are found); meristematic tissues are classified as apical, lateral, and intercalary (see the image given below).
    • Apical meristem (as shown in the above image) is present at the growing tips of stems and roots and helps in their growth.
    • Lateral Meristem is found in stem or root region and helps in their growth.
    • Intercalary meristem is found at the base of the leaves or internodes (on twigs) and helps in growth.

    Permanent Tissue

    • Cells of meristematic tissue later differentiate to form different types of permanent tissue.
    • Permanent Tissue is further categorized as −
      • Simple Permanent Tissue and
      • Complex Permanent Tissue

    Simple Permanent Tissue

    • Simple Permanent Tissue further categorized as −
      • Parenchyma
      • Collenchyma
      • Sclerenchyma
      • Epidermis
    • Parenchyma tissue provides support to plants and also stores food.
    • Sometimes, parenchyma tissue contains chlorophyll and performs photosynthesis, in such a condition, it is known as collenchyma.
    • The collenchyma tissue provides flexibility to plant and also provides mechanical support (to plant).
    • The large air cavities, which are present in parenchyma of aquatic plants, give buoyancy to the plants and also help them float, are known as aerenchyma.
    • The Sclerenchyma tissue makes the plant hard and stiff. For example, the husk of a coconut is made up of sclerenchymatous tissue.
    • The cells of Sclerenchyma tissue normally are dead.
    • The outermost layer of cells is known as epidermis.
    • The epidermis is usually made up of a single layer of cells.
    • The entire surface of a plant has the outer covering of epidermis, which protects all the parts of the plant.

    Complex Permanent Tissue

    • The complex tissue, normally, consists of more than one type of cells which work together as a unit.
    • Complex tissues help in the transportation by carrying organic material, water, and minerals up and down in the plants.
    • Complex Permanent Tissue is categorized as;
      • Xylem and
      • Phloem
    • Xylem, normally, consists of tracheid, vessels, xylem parenchyma, and xylem fibers.
    • Xylem is accountable for the conduction of water and mineral ions/salt.
    • Phloem, normally, is made up of four types of elements namely −
      • Sieve tubes
      • Companion cells
      • Phloem fibers and
      • Phloem parenchyma
    • Phloem tissue transports food from leaves to other parts of the plant.

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