Plant Tissue

In living organisms, cells specializing in a particular function are often grouped together in the body. This means that a particular function is carried out by a group of cells at a definite place in the body. This cluster of cells, called a tissue, is arranged and designed so as to give the highest possible efficiency of function. Blood, phloem and muscle are all examples of tissues in human beings. A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue. Tissue culture is a method in which fragments of tissue from an animal or plant are transferred to an artificial environment in which they can continue to survive and function.

Plant Tissues

Plants are stationary or fixed. Since they have to be upright, they have a large quantity of supportive tissue. The supportive tissue generally has dead cells. Animals, on the other hand, move around in search of food, mates and shelter and hence consume more energy as compared to plants. Most of the tissues they contain are living. Another difference between animals and plants is in the pattern of growth. The growth in plants is limited to certain regions, while this is not so in animals. There are some tissues in plants that divide throughout their life. These tissues are localized in certain regions. Based on the dividing capacity of the tissues, various plant tissues can be classified as growing or meristematic tissue and permanent tissue. Cell growth in animals is more uniform. So, there is no such demarcation of dividing and nondividing regions in animals. Plant tissue culture is defined as culturing plant seeds, organs, explants, tissues, cells, or protoplasts on a chemically defined synthetic nutrient media under sterile and controlled conditions of light, temperature, and humidity.

Types of Tissues in Plants

Tissues in plants can be broadly divided into two categories:

1. Meristematic Tissue: Plant growth takes place only in some particular regions. This is because the dividing tissue, also known as meristematic tissue, is located only at these points. Depending on the region where they are present, meristematic tissues are classified as apical, lateral and intercalary. New cells produced by meristem are initially like those of meristem itself, but as they grow and mature, their characteristics slowly change, and they become differentiated as components of other tissues. Cells of meristematic tissue are very active. They have dense cytoplasm, thin cellulose walls and prominent nuclei.

2. Permanent Tissue: Permanent tissues are defined as a group of living or dead cells formed by meristematic tissue that has lost its ability to divide and has been permanently placed at fixed positions in the plant body. Meristematic tissues that take up a specific role lose the ability to divide. They are further divided into two categories:

   1. Simple Permanent Tissue: A few layers of cells beneath the epidermis are generally simple permanent tissue. Parenchyma is the most common simple permanent tissue. It consists of relatively unspecialised cells with thin cell walls. They are living cells. They are usually loosely arranged; thus, large spaces between cells (intercellular spaces) are found in this tissue. This tissue generally stores food. In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma.

   2. Complex Permanent Tissue: The different types of tissues we have discussed until now are all made of one type of cells, which look like each other. Such tissues are called simple permanent tissue. Yet another type of permanent tissue is complex tissue. Complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function. Xylem and phloem are examples of such complex tissues. They are both conducting tissues and constitute a vascular bundle. 

Tissue culture in plants

Plant tissue culture is based on the fact that many plant cells have the ability to regenerate a whole plant. Single cells, plant cells without cell walls, pieces of leaves, stems or roots can often be used to generate a new plant on culture media given the required nutrients and plant hormones. There are many advantages of plant tissue culture over conventional propagation methods, such as the production of exact copies, quickly producing mature plants, regeneration of genetically modified plants, production of plants from seeds having very low chances of germinating, storage of genetic plant material, and clean viral infections from certain parts of the plant.

Conclusion

In living organisms, a particular function is carried out by a group of cells at a definite place in the body. This cluster of cells, called a tissue, is arranged and designed so as to give the highest possible efficiency of function. Plants have a large quantity of supportive tissue. The supportive tissue generally has dead cells. The growth in plants is limited to certain regions. There are some tissues in plants that divide throughout their life. These tissues are localized in certain regions. Tissues in plants can be broadly divided into two categories: Meristematic tissues and Permanent tissues. Permanent tissues are further divided into simple and complex permanent tissues. There are many benefits of plant tissue culture over conventional propagation.