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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 cell division. These meristematic cells play a fundamental role in plant growth, regeneration, and acclimatization, as they serve as the source ...
Traditionally, plant stem cells were thought to only exist in SAM and RAM and studies were conducted based on this assumption. However, recent studies have indicated that (pro)cambium also serves as a niche for plant stem cells: "Procambium cells fulfill the criteria for being stem cells since they have the capacity for long-term self renewal and being able to differentiate into one or more ...
Specifically, the cell division and differentiation needed for growth occurs in specialized structures called meristems. [1] [2] These consist of undifferentiated cells (meristematic cells) capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants.
Phellogen is defined as the meristematic cell layer responsible for the development of the periderm. Cells that grow inwards from there are termed phelloderm, and cells that develop outwards are termed phellem or cork (note similarity with vascular cambium). The periderm thus consists of three different layers: [1] [2]
The cells of meristematic tissue are similar in structure and have a thin and elastic primary cell wall made of cellulose. They are compactly arranged without inter-cellular spaces between them. Each cell contains a dense cytoplasm and a prominent cell nucleus. The dense protoplasm of meristematic cells contains very few vacuoles.
Parenchyma cells are often living cells and may remain meristematic, meaning that they are capable of cell division if stimulated. They have thin and flexible cellulose cell walls and are generally polyhedral when close-packed, but can be roughly spherical when isolated from their neighbors. Parenchyma cells are generally large.
The quiescent centre is a group of cells, up to 1,000 in number, in the form of a hemisphere, with the flat face toward the root tip of vascular plants. [1] It is a region in the apical meristem of a root where cell division proceeds very slowly or not at all, but the cells are capable of resuming meristematic activity when the tissue surrounding them is damaged.
The significant factors include differences in the stage of the cells in the cell cycle, the availability of or ability to transport endogenous growth regulators, and the metabolic capabilities of the cells. The most commonly used tissue explants are the meristematic ends of the plants like the stem tip, axillary bud tip, and root tip. [3]