What is plasmodesmata?

Plasmodesmata: The Secret Communication Tunnels of Plant Cells

Table of contents

what is a desmotubule?

Plasmodesmata (singular: plasmodesma) are microscopic channels that traverse the cell walls of plant cells and some algal cells, enabling transport and communication between them. There are two forms of plasmodesmata: primary plasmodesmata, which are formed during cell division, and secondary plasmodesmata, which can form between mature cells.

Similar structures called gap junctions and membrane nanotubes interconnect animal cells, and stomules form between plastids in plant cells.
A typical plant cell may have between 1,000 and 100,000 plasmodesmata connecting it with adjacent cells.

Plasmodesmata Structure

Plasmodesmata is a tube linking one cell to another. Surrounding the open space of the tube is a membrane, and running in the center is the desmotubule, which consists of tightly packed endoplasmic reticulum (ER). The ER is continuous between the two cells. Between the desmotubule and the membrane is the cytoplasmic sleeve, where most transfer of molecules occurs. The sleeve contains various structures, such as actin and myosin, which provide contractile forces that aid in transport.

Plasmodesmata Function

Plasmodesmata facilitate the movement of molecules between cells, ranging from small photosynthetic products to large proteins and mRNA. In vascular tissue, plasmodesmata are crucial for the movement of nutrients. They are also crucial during development because, unlike animal cells, plant cells do not move. The correct expression of genes both temporally and spatially is therefore important. While plant cells, like animal cells, are capable of receptor-ligand interactions to signal other cells, plasmodesmata offer direct contact. In addition, the size of the sleeve differs in different cell types and plant tissues. Plasmodesmata are therefore an active cell component in intercellular transport during development and in the mature tissue.

Importance of Plasmodesmata

Transport of substances: Nutrients and signals travel easily between cells.

Coordination: Helps cells act together during growth, repair, and defense.

Defense: Can be closed during attacks by pathogens to prevent infection spread.

Development: Crucial for embryo development and tissue differentiation.

Fun Facts About Plasmodesmata

Nature’s Internet:
Plasmodesmata are often called the "internet of plant cells" because they allow rapid, efficient communication across the entire plant!

Quick Revision Notes for Students

Heading	Key Points
Definition	Microscopic channels connecting the cytoplasm of adjacent plant cells
Function	Transport of nutrients, signals, hormones, proteins, RNA
Structure	Plasma membrane, cytoplasmic sleeve, desmotubule
Found In	Plant cells only (not animal cells)
Special Features	Can open/close; help in defense against pathogens
Discovered By	Eduard Tangl in 1879
Example	Movement of sugars from one plant cell to another during growth

What Is a Desmotubule?

The desmotubule is a narrow, tube-like structure found inside the plasmodesmata.
It is a specialized extension of the plant’s smooth endoplasmic reticulum (ER) that runs through the center of the plasmodesmatal channel.

Key Features of Desmotubule:

Originates from the smooth ER of connected cells.
Occupies the central part of the plasmodesmata.
Mainly helps in stabilizing the structure and regulating material flow.
Sometimes assists in selective transport of larger molecules between cells.

Quick Comparison Table: Plasmodesmata vs Desmotubule

Feature	Plasmodesmata	Desmotubule
Definition	Microscopic channels connecting adjacent plant cells	Central tube inside plasmodesmata derived from the smooth ER
Function	Facilitates transport of water, nutrients, and signals between cells	Supports structure and may regulate specific transport
Structure	Lined by plasma membrane, has a cytoplasmic sleeve	Narrow tube running through the center
Origin	Plasma membrane of the cell	Smooth endoplasmic reticulum (ER)
Presence	Found in plant cells only	Present inside plasmodesmata

FAQs About Plasmodesmata

❓ 1. Are plasmodesmata found in animal cells?

👉 No, they are found only in plant cells. Animal cells use gap junctions for communication.

❓ 2. What is the main function of plasmodesmata?

👉 Their main function is to allow communication and transport of substances between plant cells.

❓ 3. Can plasmodesmata be opened or closed?

👉 Yes, plants regulate plasmodesmata by widening, narrowing, or blocking them when necessary.

❓ 4. How are plasmodesmata different from gap junctions?

👉 Plasmodesmata cross thick plant cell walls; gap junctions connect soft animal cell membranes.

❓ 5. Who discovered plasmodesmata?

👉 Eduard Tangl discovered plasmodesmata in 1879 while studying plant tissues.

❓ 6. What is the function of plasmodesmata in the phloem?

👉 In the phloem, plasmodesmata help transfer sugars (like sucrose) and other nutrients from companion cells to sieve tube elements.
They ensure efficient loading and unloading of materials during the plant’s nutrient transport process, known as translocation.

❓ 7. Are plasmodesmata found in prokaryotic or eukaryotic cells?

👉 Plasmodesmata are found only in eukaryotic cells, specifically in plant cells.
They are microscopic channels that connect the cytoplasm of adjacent plant cells through their thick cell walls—a unique feature of plants.
Prokaryotic cells do not have plasmodesmata, as they lack a true cell wall structure like plants and are structurally simpler.

References

Evert, R. F., & Eichhorn, S. E. (2006). Raven Biology of Plants (7th ed.). W.H. Freeman and Company.
Taiz, L., Zeiger, E., Møller, I. M., & Murphy, A. (2015). Plant Physiology and Development (6th ed.). Sinauer Associates.
Roberts, A. G., & Oparka, K. J. (2003). Plasmodesmata and the control of symplastic transport. Plant, Cell & Environment, 26(1), 103–124. https://doi.org/10.1046/j.1365-3040.2003.00950.x
Faulkner, C. (2018). Plasmodesmata and the symplast. Current Biology, 28(3), R137–R141. https://doi.org/10.1016/j.cub.2017.11.059
Zambryski, P., & Crawford, K. (2000). Plasmodesmata: Gatekeepers for cell-to-cell transport of developmental signals in plants. Annual Review of Cell and Developmental Biology, 16, 393–421. https://doi.org/10.1146/annurev.cellbio.16.1.393
Alberts, B., Johnson, A., Lewis, J., et al. (2002). Molecular Biology of the Cell (4th ed.). Garland Science.
Encyclopedia Britannica. (n.d.). Plasmodesmata. Retrieved from https://www.britannica.com/science/plasmodesma
Biology Online. (2023). Plasmodesmata Definition and Function. Retrieved from https://www.biologyonline.com/dictionary/plasmodesmata

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