What are simple tissues? Describe various types of simple tissues.
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There are 3 types - parenchyma, collenchyma and sclerenchyma.
Paremchyma is very simple. It stores water and nutrition. It is a living tissue. It is present in mesophyll of the leaf.
Collenchyma has lignin deposition. It is a living tissue. It is present in the stem.
Sclerenchyma is dead tissue. It has pectin deposits. It is present in the covering of nuts.
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A group of cells which are similar in origin; similar in structure and similar in function are called simplepermanent tissue.
or
The homogeneous group of non-meristematic or permanent cells having similar structure, function and origin is collectively known as simple tissue.
Parenchyma
The Parenchyma is walled living cells. It is very soft in nature because of the presence of thin walled cells.
Origin : It usually develops from ground meristems. The parenchyma of vascular bundle develops from procambium ; but that of secondary vascular tissues develop from inter-fascicular cambium. The parenchyma of secondary epidermis is formed from phellogen or cork cambium.
Structures of Parenchyma :
The simple tissue, parenchyma shows the following characteristics: -
(1) They are living cells with thin cellulose wall, though secondary xylem. Parenchyma tissue are lignified as observed in the endosperm of date-palm.
(2) They are with equal diameter, more or less spherical or star shaped in Scirpus, and usually with intercellular spaces.
(3) The cells contain large nucleus and large vacuoles.
(4) They are either photosynthetic or non-photosynthetic, containing leucoplasts.
Collenchyma
The permanent simple tissue consisting of unevenly thick walled living cells are called collenchymas. The uneven thickening of these cell walls makes it partially hard giving mechanical support. It is derived mostly from the elongated cells of the ground meristem and sometimes from the procambium.
Structure of collenchyma:
This type of simple tissue shows the following characteristics:
(1) The living cells with unevenly thickened walls composed of hemicellulose and pectin.
(2) The cells are elongated containing scanty vacuolated rotoplasm, appear polygonal in cross section.
(3) They are constituted by short and long fibre like cells, the short cells remain ong the long axis but the long cells are interlocked with overlapping tapering end.
(4) The primary pit fields are present.
(5) The intercellular spaces may or may not be present.
(6) They may contain chloroplast, helping in photosynthesis.
sclerenchyma
The permanent simple tissue consisting of evenly thick-walled dead cells are named sclerenchyma. They are very hard and heavily lignified in nature.
Structure of sclerenchyma:
The sclerenchyma cells show the following characteristics:
(1) The cells are heavily thickened with lignified walls, simple pits and small lumen.
(2) The cells are dead without protoplasm.
(3) The cell walls with very low water content.
(4) Their shapes and sizes vary
or
The homogeneous group of non-meristematic or permanent cells having similar structure, function and origin is collectively known as simple tissue.
Parenchyma
The Parenchyma is walled living cells. It is very soft in nature because of the presence of thin walled cells.
Origin : It usually develops from ground meristems. The parenchyma of vascular bundle develops from procambium ; but that of secondary vascular tissues develop from inter-fascicular cambium. The parenchyma of secondary epidermis is formed from phellogen or cork cambium.
Structures of Parenchyma :
The simple tissue, parenchyma shows the following characteristics: -
(1) They are living cells with thin cellulose wall, though secondary xylem. Parenchyma tissue are lignified as observed in the endosperm of date-palm.
(2) They are with equal diameter, more or less spherical or star shaped in Scirpus, and usually with intercellular spaces.
(3) The cells contain large nucleus and large vacuoles.
(4) They are either photosynthetic or non-photosynthetic, containing leucoplasts.
Collenchyma
The permanent simple tissue consisting of unevenly thick walled living cells are called collenchymas. The uneven thickening of these cell walls makes it partially hard giving mechanical support. It is derived mostly from the elongated cells of the ground meristem and sometimes from the procambium.
Structure of collenchyma:
This type of simple tissue shows the following characteristics:
(1) The living cells with unevenly thickened walls composed of hemicellulose and pectin.
(2) The cells are elongated containing scanty vacuolated rotoplasm, appear polygonal in cross section.
(3) They are constituted by short and long fibre like cells, the short cells remain ong the long axis but the long cells are interlocked with overlapping tapering end.
(4) The primary pit fields are present.
(5) The intercellular spaces may or may not be present.
(6) They may contain chloroplast, helping in photosynthesis.
sclerenchyma
The permanent simple tissue consisting of evenly thick-walled dead cells are named sclerenchyma. They are very hard and heavily lignified in nature.
Structure of sclerenchyma:
The sclerenchyma cells show the following characteristics:
(1) The cells are heavily thickened with lignified walls, simple pits and small lumen.
(2) The cells are dead without protoplasm.
(3) The cell walls with very low water content.
(4) Their shapes and sizes vary
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