Meristem

In cell biology, the meristem is a structure composed of specialized tissue found in plants, consisting of stem cells, known as meristematic cells, which are undifferentiated cells capable of continuous cellular division. These meristematic cells play a fundamental role in plant growth, regeneration, and acclimatization, as they serve as the source of all differentiated plant tissues and organs. They contribute to the formation of structures such as fruits, leaves, and seeds, as well as supportive tissues like stems and roots.

Meristematic cells are totipotent, meaning they have the ability to differentiate into any plant cell type. As they divide, they generate new cells, some of which remain meristematic cells while others differentiate into specialized cells that typically lose the ability to divide or produce new cell types. Due to their active division and undifferentiated nature, meristematic cells form the foundation for the formation of new plant organs and the continuous expansion of the plant body throughout the plant's life cycle.

Meristematic cells are small cells, with thin primary cell walls, and small or no vacuoles. Their protoplasm is dense, filling the entire cell, and they lack intercellular spaces. Instead of mature plastids such as chloroplasts or chromoplasts, they contain proplastids, which later develop into fully functional plastids.

Meristematic tissues are classified into three main types based on their location and function: apical meristems, found at the tips of roots and shoots; intercalary or basal meristems, located in the middle regions of stems or leaves, enabling regrowth; and lateral meristems or cambium, responsible for secondary growth in woody plants.