Key Difference – Apical vs Lateral Meristems
Let us first understand what a meristem is, before looking at the differences between apical and lateral meristems. Meristem is a unique plant tissue made of cells that are not fully differentiated and capable of dividing continuously to produce new plant tissues. In addition, these cells possess some other general characteristic features, which include the presence of cube-shaped cells with dense cytoplasm, one or more prominent nuclei, small vacuoles in the cytoplasm, plastids in proplastid stage, presence of homogenous, thin cell walls made up of cellulose, and the absence of intercellular spaces and ergastic matter. Since these cells have the power of division, their metabolic rate is very high compared to the cells in other plant tissues. Classification of meristems is done mainly based on their origin, developmental stages, structure and task. There are three types of meristems according to their position in a plant, namely; apical meristem, intercalary meristem, and lateral meristem. The key difference between apical and lateral meristem is, apical meristem helps in the primary growth of a plant whereas lateral meristem helps in the secondary growth of a plant.
What is Apical Meristem?
Apical meristems are positioned at the apices of stems, roots and their lateral branches. This meristem is responsible for the vertical growth of the plant along its axis. The apical meristem is dome-shaped and has two parts; the outer layer (tunica) and the inner mass (corpus). It is composed of a small mass of cells and produces the primary permanent tissues of plants (primary growth) including epidermis, xylem, phloem, and ground tissues. The root apical meristem is covered by a protected layer of cell called the root cap. The cells of apical meristem possess all the general characteristic features of the meristem. The shoot apex is quite different from the root apex. The shoot apical meristem gives rise to leaf primordia (which cover and protect the shoot apical meristem), and bud primordia.
What is Lateral Meristem?
Lateral meristems consist of the vascular cambium and cork cambium and is responsible for the secondary growth of plant tissues.The secondary growth increases the girth of the plant (horizontal growth). Lateral meristem is found along the entire length of the stem and root except at apices. In a cross section of stem or root of a plant that undergoes secondary growth, the lateral meristem can be seen as rings.
What is the difference between Apical and Lateral Meristems?
Definition of Apical and Lateral Meristem:
Apical meristem: A plant tissue with undifferentiated cells found at the tip of a shoot or root and is responsible for the primary growth.
Lateral meristem: A plant tissue with undifferentiated cells that is found along the length of stems and roots and is responsible for the secondary growth.
Features of Apical and Lateral Meristem:
Apical meristem: Apical meristems are positioned at the apices of stems, roots, and their lateral branches.
Lateral meristem: Lateral meristems are found along the entire length of stem and root except at apices.
Apical meristem: Primary growth takes place at apical meristems.
Lateral meristem: Secondary growth takes place at lateral meristems.
Apical meristem: Apical meristem increases the length of a plant along its vertical axis,
Lateral meristem: Lateral meristem increases the girth of a plant.
Apical meristem: Apical meristem gives rise to lead primordia and bud primordia, unlike lateral meristem.
Lateral meristem: Lateral meristems consist of the vascular cambium and cork cambium, unlike the apical meristem.
Apical meristem: Apical meristem gives rise to primary permanent tissues including epidermis, xylem, phloem, and ground tissues.
Lateral meristem: Lateral meristem gives rise to wood, inner bark and outer bark.
Image Courtesy: “Apical Meristems in Crassula ovata” by Daniel,levine – Digital Camera.(CC BY-SA 3.0) via Wikipedia “Japanese Maple Bark” by David Shankbone- Own work. (CC BY-SA 3.0) via Commons