You will only find plasmodesmata in plant cells. It’s plasmodesmata that is responsible for letting plant cells share substances, materials, and molecules from cell to cell.
Plasmodesmata have been compared to the bridges that connect fortresses together. In this case, the fortress would be the plant cell walls.
Plants have both a primary and secondary cell wall and plasmodesmata are designed to bridge both walls and create a kind of pathway between cells.
Plant cells are designed differently than animal cells. Plant cells have cell walls that are actually organelles.
Their purpose is to provide the rigidity needed for the cells of the plant so that it can stand up to wind, rain, and many other forces.
The cell walls surround the cell membranes and are around 0.1-10 micrometers thick.
There’s a main problem when you have a cell wall designed for protection: it’s rough to get things in and out of the cell and allow communication from cell to cell.
This is where plasmodesmata becomes a major player. Plasmodesmata is the bridge and messenger that can take waste outside of the cell as well as bring the needed food in.
Plasmodesmata can act as a communication bridge.
Just as any bridge must have two ends that are well-anchored, plasmodesmata can’t do its job unless the plant cells provide an anchored place by touching.
To be the best communicator and transport substances, plasmodesmata starts with two nearby cells.
Once a substance such as a well-needed protein is supplied to a neighbor cell it will continue to distribute proteins to all other cells because they are linked together by touching.
Plasmodesmata act as both a bridge and a support system for all of the touching plant cells.
This kind of massive communication and distribution requires a lot of plasmodesmata and in the situation of two plant cells that are touching, you can find from 1,000-100,000 plasmodesmata.
It’s thanks to plasmodesmata that nutrients are shared and waste removed from each of the plant cells. If there wasn’t any plasmodesmata, there wouldn’t be a balance in the plant and the cells would die.
Given the unusual and yet really important job that plasmodesmata have, scientists have been curious as to what their appearance is.
Under a high-powered microscope you can see that they are shaped like cylinders and that plasmodesmata have a plasma membrane lining.
The lining is important because this is similar to the cell membrane and it gives them the ability to connect with the membrane in a continuous way.
Most of the plasmodesmata contain “desmotubules”, which are thin, tube-like structures that play a part in connecting the cells.
While the desmotubules make up a large percentage of the plasmodesmata, it isn’t all of it.
It has a ring of cytoplasm that it shares between the plasmodesmata and the inside surface of a channel that is membrane-lined.
When a cell goes through its division to create new cells, part of the parent cell’s endoplasmic reticulum is trapped in the newly forming cell wall that is made for the creation of the daughter cells and this becomes the plasmodesmata.
In the formation to connect daughter cells, there may be thousands of plasmodesmata created.
Scientists believe that plasmodesmata pass nutrients in and take waste out of the cell by the process of dilating (opening) and constricting (closing) their ends.
In this way they can not only act as a bridge between the cells but also as a kind of traffic cop to make sure the right amounts of salt, sugars, and amino acids get through but not most of the larger molecules.
Scientists have noted that there are exceptions to the size restrictions that plasmodesmata have. In some cases they have seen the binding of special proteins, viruses, and the plasmodesmata to open the diameter of the channels to allow larger molecules passage.
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