Each tiny cytoplasmic channel, known as a plasmodesma, that connects a live cell to its next living cell in a higher plant is able to pass through the walls of the intervening cells.
They function as cell wall tunnels that allow the cells in a tissue communicate with one another.
Each plasmodesma connects the plasma membrane to that of its neighbor.
They develop around components of the smooth endoplasmic reticulum that become caught in the new cell wall that will split the parent cell during cytokinesis (during mitotic cell division). Here, the wall is not further thickened; instead, pit-like depressions or thin spots develop in the walls.
Pits typically form pairs between neighboring cells.
They can also be implanted between non-dividing cells in existing cell walls (known as secondary plasmodesmata).
The occurrence of the plasmodesma can be found vary depending on several factors.
For instance, the walls of the columns of cells that lead to areas of strong secretion, such as nectar-secreting glands, are particularly frequent and profuse with plasmodesmata (trichomes of Abutilon nectaries).
In contrast to ordinary cell walls, which typically have fewer than 1 plasmodesmata per square micrometer those of these cells can have 15 or more.
A normal plant cell may have 1 to 10 plasmodesmata per μm2, or 10^3 to 10^5 plasmodesmata linking it with neighboring cells.
They have membrane-lined, generally cylindrical channels that range in size from 20 to 40 nm.
The plasma membrane, the cytoplasmic sleeve, and the desmotubule are the three primary layers that constitute them.
The desmotubule, a more slender cylindrical structure that connects linked cells cell to cell via the center of most plasmodesmata, continues to be continuous with components of each connected cell’s SER membrane.
An annulus of cytosol, which frequently seems to be constricted at each end of the plasmodesmata, exists between the exterior of the desmotubule and the interior face of the cylindrical plasma membrane.
The flow of molecules across the annulus connecting the two cytosols may be regulated by these constrictions.
The phospholipid bilayer structure of the plasmodesma’s plasma membrane, which is a continuous extension of the cell membrane or plasmalemma, is comparable.
Functions of Plasmodesmata
They are tiny passageways that serve as cytoplasmic bridges between plant cells, facilitating communication and material movement. They link the plant’s symplastic space and are highly specialized channels that permit the transport of water, different nutrients, and other chemicals between cells.
Plasmodesmata play a role in intercellular communication by enabling direct molecular communication between cells.
According to certain theories, plasmodesmata act similarly to animal cell gap junctions in mediating transport between neighboring plant cells. Molecules with molecular weights of under 800 Daltons can flow through them.
From one cell to the next, plasmodesmata have been seen to transfer proteins (including transcription factors), messenger RNA, viroid, and viral genomes.
Cells in the phloem also employ plasmodesmata, and companion cells control the sieve-tube cells by symplastic transport.