The area of tissue from which new growths are formed in plants is called meristem. The cells at meristem continually proliferate and do not differentiate. The new leaves arise from the meristem tissue, which depends upon the signals received by it. It also gives rise to flowers or roots of the plant. A plant cannot produce new cells without the meristem.
Apical Meristem Function
The apical meristem is responsible for the growth of the plant and its length and height. The location of apical meristem is at the ends of roots, known as root apical meristem, or at the tops of shoots, which are known as shoot apical meristem.
This meristem is responsible for the primary growth of the plant. The vertical growth is promoted by the axillary buds, which are exerted by the presence of an apical bud.
Shoot Apical Meristem Function
The shoot apical meristem is developed to become one of three primary meristems that are the protoderm, ground meristem, and procambium. The shoot apical meristem is mainly composed of undifferentiated cells found above the ground.
The epidermal tissues of the plant are formed by the protoderm while the ground develops into the cortex and pith of the plant. And the xylem and phloem, collectively known as vascular bundles are formed by the procambium.
The leaves of the plant are also included in the shoot that grows from the sides of the apical meristem. A bump or an axillary bud is formed by the beginning growth of the leaf at the node.
The axillary bud remains dormant if the terminal bud is in close proximity to it. However, the increased distance or removal of the terminal bud results in the disappeared or diminished exerting apical dominance.
It allows the growth of leaves at the lateral buds of the apical meristem. The shoot apical meristem converts into the inflorescence meristem when the angiosperm plant becomes ready to bloom and emerge various flower parts such as petals, sepals, stamens, carpels, etc.
Root Apical Meristem
It is found below the ground. The root apical meristem is responsible for the growth and development of a plant’s root. The root apical meristems have the ability to yield two types of tissues at the same time and can produce cells in a bilateral direction.
Among these two types of tissues, one typically comprises the main roots of the plant and the other type consists of a root cap, the main roots are responsible for continuous growth and supply proliferative, undifferentiated cells for continued growth while the root cap protects the apical meristem.
As the root cap grows deeper into the soil, the cells of the root cap are continuously being shed and replaced by new cells, which are provided by the main root. This is typical of the taproot.
The lateral growth of the root is conducted by the lateral root meristem, which helps in efficient water supply and nutrient absorption in the plant. It also helps in nutrient storage and stability for aerial growth.
Basal Meristem Function
Basal meristem is also called intercalary meristem. It is located between mature, differentiated tissues. The intercalary meristem is distinctly different from the apical meristem, which is located relatively near an apical meristem.
The vertical growth of the plant is promoted by the apical meristem and the intercalary meristem works independently of the apical meristem. However, it works in the base of the plant, not at the tip of the plant tip. The grasses and other plants can grow continuously after being cut due to the intercalary meristem.
Lateral Meristem Function
The vertical growth of the plant is controlled by the apical meristem, similarly, the lateral meristem is responsible for the lateral growth of the plant. Lateral growth is also known as secondary growth.
The lateral growth is conducted around an already established stem thus it is known as secondary growth. There are two types of lateral meristem in woody plants, named the vascular cambium and the cork cambium.
The vascular cambium is similar to the procambium of the apical meristem, which is responsible for the development of wood and increased width of the plant. The periderm is developed from the cork cambium, similar to the protoderm.
The primary epidermis growth is produced from the protoderm. And the epidermis is replaced by periderm to produce bark, which acts as a shield and protects the plant from physical damage and water loss by a waxy layer of suberin.