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Introduction |
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A tissue is an aggregation of cells that have a common origin and structure, and perform similar functions. Tissues are meant for meeting the physical and physiological needs of the plant body. |
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Meristematic Tissue (Meristem) |
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The meristematic tissue is formed exclusively by undifferentiated or embryonic cells. These cells, known as meristematic cells, are responsible for bringing about growth of the plant body due to their capacity to undergo continuous mitotic divisions. |
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Permanent Tissues (Mature Tissues) |
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The permanent tissues are formed by the differentiated cells, which become specialised to perform specific functions like protection, support, storage and conduction. The permanent tissues always differentiate from the meristematic cells, during the process of growth. |
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Simple Permanent Tissues |
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These tissues are described as homogenous, since the constituent cells are identical in their structure. |
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Parenchyma |
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It is the main tissue in the plant body, occurring in almost all regions. It is particularly abundant in the root and stem. It is the least specialised among the permanent tissues. The cells of the tissues are called parenchyma cells. These cells are usually spherical or oval in shape. Sometimes the cells may be elongated. Very rarely, the cells become irregular in shape. They are usually loosely arranged with prominent intercellular spaces. In certain regions like epidermis, the cells become compactly arranged and hence, intercellular spaces are absent. |
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Collenchyma |
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It is a type of simple permanent tissue, which is mainly meant for providing mechanical support to the shoot system of a plant. Collenchyma is completely absent in the root. |
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Sclerenchyma |
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It is a type of simple permanent tissue mainly meant for providing mechanical support and protection to different parts of the plant body. Hence, sclerenchyma occurs in all the parts of the plant body, including the fruit and seed. |
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Complex Permanent Tissues |
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These tissues are characterised by the presence of dissimilar cells. Hence, they are described as heterogenous in their cellular composition. |
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Xylem |
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It is a complex permanent tissue, which is specialized for the conduction of water and mineral substances in the plant body. Xylem is a heterogenous tissue made up of four different types of cellular elements. |
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Phloem |
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Phloem is a complex permanent tissue, which is specialized for the conduction of food and other organic substances. Phloem is also a heterogenous tissue. |
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Tissue Systems in the Plant Body |
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The epidermis usually forms projections known as epidermal hairs. In the root, the epidermal hairs are unicellular and are called as root hairs. The root hairs penetrate between the soil particles to absorb water. In the stem and the leaf, the epidermal hairs are multicellular and are known as trichomes. They are involved in the secretion of some terpenoid compounds. |
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Plant Anatomy - Anatomy of a Typical Young Dicot Stem |
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Epidermis is the outermost covering of the stem. It is represented by a single layer of compactly arranged, barrel-shaped parenchyma cells. Intercellular spaces are absent. The cells are slightly thick walled. Epidermis shows the presence of numerous multicellular projections called trichomes. Externally, a thin transparent waxy covering called cuticle, which prevents excessive evaporation of water, surrounds the epidermis. The epidermis also contains numerous minute opening called stomata, which are mainly involved in transpiration. |
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Anatomy of a Typical Monocot Stem |
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Epidermis is the outermost covering of the stem represented by a single layer of compactly arranged, barrel-shaped parenchyma cells. Intercellular spaces are absent. Trichomes are absent. A cuticle is present. The epidermis contains numerous minute openings called stomata. |
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Difference Between Dicot Stem and Monocot Stem |
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Differentiated into cortex, endodermis, pericycle, medullary rays and pith. |
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Anatomy of a Typical Dicot Root |
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Epiblema is the outermost covering of the root formed by single layer of compactly arranged, barrel-shaped, parenchyma cells. The cells are characteristically thin-walled since they are involved in absorption of water. A cuticle and stomata are absent. Some of the epiblema cells are produced into long unicellular projections called root hairs. Hence, the epiblema is also known as piliferous layer. |
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Anatomy of a Typical Monocot Root |
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Epiblema is the outermost covering of the root formed by a single layer of compactly arranged, barrel-shaped parenchyma cells. The cells are characteristically thin-walled since they are involved in absorption of water. A cuticle and stomata are absent. Some of the epiblema cells are produced into long unicellular projections called root hairs. Hence, epiblema is also known as piliferous layer. |
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Differences between a Dicot root and a dicot stem |
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Circular in appearances. Contains passage cells and casparian strips. |
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Anatomy of the Leaf |
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Leaf represents an important part of the plant body. It is involved in vital physiological activities such as transpiration, respiration and photosynthesis. Unlike the stem and the root, the leaf is flat and hence, the anatomy of the leaf differs very much from that of stem or root. |
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Secondary Growth |
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The normal process of growth that occurs in every plant body is known as primary growth. It is the result of the activity of primary meristem. The process of primary growth results in the formation of primary permanent tissues such as primary xylem, primary phloem and primary cortex. However in the dicot plants, there is a process of growth that begins after a known period of primary growth. Such a growth is known as secondary growth. It is the result of the activity of secondary meristem. It results in the formation of secondary permanent tissues such as secondary xylem, secondary phloem and secondary cortex. As a result, secondary growth brings about an increase in the girth of the plant body. |
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Summary |
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An angiosperm plant body is composed of two basic types of tissues namely meristematic and permanent tissues. Meristematic tissue is formed by undifferentiated, embryonic cells called meristematic cells. |
