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Tuesday, February 14, 2012

The Huge Exploration of Tissues of Plants According to the Structure and Functions

After very long time I'm again going to keep SmartSciencePro active. I was busy wit my life. Ok then here I'm going to the post.

Introduction

Now you know about the organization of organelles in a cell. The organelles in the cell vary according to the functions they accomplish. the cells of similar structure compact together, can be seen in multicellular organisms to accomplish a particular function. A group of cells showing similarities in growth and origin, and adapted to fulfill very special matters, is known as a tissue. There are a number of various tissues in muticellular organisms for division of labour and their structures are adapted according to the functions.

Plant Tissues

There are two types of tissues.
  1. Meristematic Tissues.
  2. Permanent Tissues.
Meristematic tissues are composed of cells with the ability of dividing. It's present in the apex of the stems and the roots. Later these tissues modify into permanent tissues.

There are two types of permanent tissues.

1. Simple Permanent Tissues.
  • Parenchyma.
  • Collenchyma.
  • Sclerenchyma.
2. Complex Permanent Tissues.
  • Xylem.
  • Phloem

1. Parenchyma Tissue

These are living cells elongated or spherical in shape. The cell wall is made up of cellulose, hemicellulose and  pectin. Intercellular air spaces are present within the tissues. These cells act as a packing tissue like in the central pith and outer cortex of young stem and roots. The osmotic properties of parenchyma cells are important, when turgid they become tightly packed and provide support. These tissues are seen in stem tuber of potato as food storage tissues. Specialized parenchymatous tissues are epidermal cells, guard cells, parenchyma in the leaf blade, endodermic cells, pericycle and companion cells.

2. Collenchymatous Tissue

Collenchymatous tissues are composed of living cells of polygonal in shape. The corners of the cell walls are thickened with cellulose. Therefore these cells are modified to supply the mechanical energy and give support.

3. Sclerenchymatous Tissue

Sclerenchymatous tissues have elongated cells with thickened cell walls by lignin. These tissues provide support and strength for the plant because they are heavily thickened with deposits of lignin. Some areas where lignin is not deposited are called simple pits, The neighbouring cells are interconnected through these minute pits. These cells are arranged as sheets to make tissues. The fibers are found in the shells of coconut and in the stem, some fibers are formed into solid rods. All are formed by sclerenchyma cells.

There are some other types of sclerenchyma cells called stone cells which are thickened by lignin. In the flesh of a pear fruit, they occur in small groups and are responsible for the'grittiness' of these fruits.
Sectional Views of Simple Plant Tissues
Sectional Views of Simple Plant Tissues

4. Xylem Tissue

The major function of the xylem tissue is the conduction of water and mineral salts. It consists of four cell types, namely tracheids, vessel elements, parenchyma and sclerenchyma.

Tracheids and Vessels

Trachieds are single cells that are elongated and lignified. Structures called simple pits appear in the walls where lignin is not thickened. Water passes to tracheid through the pits membranes continuously. The walls of tracheids are lignified as annular or spiral. The cells of vessels are long and cylindrical. The cell walls are lignified as annular, spiral, scalariform or reticulate. Water can pass through vessels with minimal obstruction as cross walls are absent. The length of a vessel may be a few centimeters, some time it may be a few meters. The walls of the cell have high tensile strength which is another important feature.

Xylem Parenchyma and Xylem Sclerenchyma

These cells are similar to parenchyma an sclerenchyma and situated mixed with tracheid and vessels. Xylem fibers provide extra energy to the xylem. They form a radial sheet of tissue called medullary ray which maintains a living link through the wood between the pith and the cortex.

5. Phloem Tissue

There arr five cell types in the phloem namely, sieve tubes, companion cells, parenchyma, fibers and sclereidons. Sieve tubes are long, tube like structures that translocate the solutions of food throughout the plant,

They are formed by end to end fusion of sieve tube elements. The sieve cells have no nuclei and the cytoplasm becomes confined to this layer around periphery of the cell. The sieve tube cell with the adjacent companion cells from a functional unit. The two adjoining sieve tube cells form a sieve plate. The phloem parenchyma cells which form the medullary rays are similar to xylem parenchyma Phloem fibers and stone cells help to maintain the strength.

I think the post is very long, but the information is much. In the next article I'll bring you about Animal Tissues with a great coverage.How about this one? Great! Awesome! Or Nice Then just share with your friends and Comment your Idea Below. Appreciate it!

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