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The entire living organism is made up of a cell. The cell is the functional and structural unit of life. Living organism is either made up of a single cell called unicellular organism or of many cells called a multi-cellular organism. When the cells having a similar origin, structure and function unite and act as a single unit, it is called tissue. Tissue simply defined as the group of cells having similar structure, origin and function. The organized group of tissue helps to form different organs. Each cell has a definite function. The function of different cells is different from each other.
A tissue is defined as the “a group of cells having a similar origin, structure, and function.” The different types of plant tissue are grouped under the following three heading:
Those tissues which are composed of immature or not well develop cells are called Meristematic tissue. These types of tissue are responsible for the cell division. So, this tissue is a group of cells that are in a continuous state of division or retain their power of division. Some of the characteristics of Meristematic tissue are as follows:
Meristematic tissue is also classified into types on the basis of their origin, position and function. They are described below:
They are divided into three types according to the origin are divided into three types. They are as follows-
They are divided into following three types on the basis of their position-
Instead of using the term apical meristem of the shoot and apical shoot of the root, it is easy to use the term shoot apex and root apex.
Meristem is divided into following three types on the basis of their functions-
In 1924, Schmidt proposed Tunica-Corpus Theory. According to this theory, leaf primordia protect the done shaped shoot apex which can distinguish into outer mantles such as tunica and inner cellular mass is known as the corpus.
The shoot apex is divided into three regions according to Histogen theory purposed by Hanstein In 1870. They are:-
In 1914, Haberlandt proposed the nomenclature of protoderm for dermatogens, ground meristem for periblem and Procambium for pleurome.
Generally, root apex is found at the tip of the main root as well as other branched roots. Root cap covers it and protects it from the injury. It is divided into other five regions. They are:-
According to the Histogen Theory shoot apex and root apex has three histogens:
1. A tissue is defined as the “a group of cells having a similar origin, structure, and function.”
2. The meristems which are origin from the embryo are called Promeristem.
3. The meristem which is originated from Promeristem is called primary meristem.
4. These meristems are found at the lateral side of the stem or along the stem.
5. In dicot plants, protoderm helps to form epidermis or epiblema and root cap.
6. Dermatogen is responsible for the formation of epiblema and root cap in dicot plants..