Meristematic tissue - Types on the basis of Position and origin

Tissue is a group of cells which are similar in function and have a common origin. Their cells are similar or may be in different types. Tissue occurs in all parts of the plant. The term tissue in plants was first coined by N. Grew.

On the basis of characteristic of the cell division, Plant tissue are of the two types Meristematic and permanent. In this Article we will discuss the meristematic tissue. 

A meristematic  tissue is a simple tissue with embryonic cells which undergo mitosis and for new cells and tissue. 

In embryos all the cells are capable of cell division therefore  all cells are meristematic soon the growth becomes restricted to a Certain  region but some  tissue still have capacity of cell division and is called meristematic tissue.

Feature of meristematic cells 

Cells  are small and thin walled. Cells are compactly arranged. Intercellular spaces are absent. Cell wall  is made up of cellulose and Pectin. Nucleus is large. The central vacuole is absent but in some cells small vacuoles are present.The cytoplasm is dense. 

Types of Meristem on the basis of origin 

On the basis of the origin, meristem can be  primary and secondary. 

Primary Meristem is derived directly from meristems of embryos or one of its derivatives. The cells  of this meristem are small isodiametric with small vacuoles. They produce primary tissue and growth in the plant. It is the primary Meristem which resemble Secondary Meristem in structure and function. This  meristem is primarily responsible for the primary growth of the plant. Apical and intercalary are examples of primary meristem. 

Secondary meristem  is generally formed from a permanent cell of a plant through the process of dedifferentiation. Secondary Meristem is also called Lateral Meristem which is primarily responsible for the secondary growth. It increases the plant in Girth. Its cells are  usually elongated with Central vacuole. This issue is produced by a Secondary Meristem called the secondary tissue. Vascular and cork cambium are examples of secondary meristem. 

Types of Meristem on the basis of position. 

Meristem can be apical, intercalary and Lateral Meristem. 

Apical Meristem are located at the growing points of stem, root and their branches. An apical Meristem has two part Promeristem and partly differentiated meristematic zone. Promeristem  is an undifferentiated part of an apical Meristem which consists of an apical initial. The partial differentiated zone is located below the apical initial. It forms three types of meristematic strip - the Dermatogen periblem  and plerome.

Apical Meristem provides growth for plants in length. They also produce axillary bud, intercalary meristem and interfascicular cambium. 

Intercalary meristem is a remaining part of apical Meristem which come to lie in between areas of permanent tissue. They are located above the node like Grasses.  be the base of the leaf like Pinus. Intercalary Meristem takes part in longitudinal growth of internode and leaves.

Lateral Meristem undergoes periclinal division and produces secondary tissue on the outer and inner side of the organ. These meristems are  responsible to increase Girth of the plant organ. The various Lateral Meristem are vascular cambium cork cambium in Dicot plants and Gymnosperm. In monocot plant accessory cambium is also an example of Lateral Meristem.

Types of Meristem on the basis of position:

Protoderm is the outer plant tissue and forms the epidermis.

And  protects the plants from any mechanical shocks.

Procambium is the innermost tissue and leads in the rise to xylem and phloem. It helps in the transport of water and nutrients to different parts of the plant.

Ground Meristem are large with thick walls and  form the cortex, pericycle, and pith.