The communicating junction linking adjacent cells in plants, which permits small molecules to pass from cell to cell while blocking most large molecules, is (3) Plasmodesmata.

Plasmodesmata are microscopic cytoplasmic channels that traverse the thick plant cell walls, connecting the cytoplasm of neighboring cells. They are lined by the plasma membrane and contain a central tubular structure called the desmotubule. This structure allows the direct exchange of water, ions, small metabolites, and signaling molecules, enabling symplastic communication. The plasmodesmata regulate passage sizes, generally allowing molecules smaller than about 800 daltons to pass freely, while restricting larger molecules.​

Unlike animal cells that use gap junctions for similar cell-to-cell communication, plants rely on plasmodesmata due to their rigid cell walls.​

Overview

• Plasmodesmata are channels that directly connect plant cell cytoplasms through cell walls.

• They permit passage of small water-soluble molecules, ions, and signaling compounds.

• Plasmodesmata are essential for developmental coordination, nutrient transport, and defense signaling in plants.

Comparative Function

Conclusion

Plasmodesmata play a unique and critical role in plant cell communication, making them the equivalent of animal cell gap junctions but structurally adapted to overcome the plant cell wall barrier while allowing selective molecular passage between cells.​