Which one of the following is the communicating junction linking adjacent cells in plants, which permits small molecules to pass from cell to cell while blocking the passage of most large molecules?

Correct option is C

The correct answer is Plasmodesmata. Plasmodesmata are channels that connect plant cells, enabling the direct transfer of small molecules such as ions, hormones, and nutrients between adjacent cells. These channels are formed by the fusion of the cell membranes and the endoplasmic reticulum of adjacent cells, allowing for communication and material exchange. Plasmodesmata are selective in terms of size and can restrict the passage of large molecules, thus ensuring that only smaller molecules pass through while larger molecules are blocked.

Information Booster

1. Plasmodesmata are specialized intercellular connections in plant cells that facilitate the movement of materials between cells.
2. These channels allow for the passage of small molecules such as water, ions, and sugars, while preventing the movement of larger macromolecules.
3. Plasmodesmata are formed by the fusion of the plasma membranes and endoplasmic reticulum of neighboring plant cells.
4. The presence of desmotubules (a structure formed by the endoplasmic reticulum) inside the plasmodesmata restricts the passage of larger molecules.
5. The selective permeability of plasmodesmata helps maintain cellular integrity and communication while controlling the movement of substances within plant tissues.
6. The regulation of plasmodesmata can be influenced by cellular signaling mechanisms that respond to plant growth conditions and environmental stimuli.

Additional Information

• Option (a): Adherens junction is a type of junction found in animal cells that helps anchor cells together, providing structural integrity. However, it does not facilitate communication between cells, making it incorrect in this context.
• Option (b): Gap junctions are the communication channels in animal cells, allowing ions and small molecules to pass between adjacent cells. They are not found in plant cells and are incorrect for this question.
• Option (d): Hemidesmosomes are structures that anchor cells to the extracellular matrix and do not serve as communication junctions. They are incorrect because they do not facilitate molecular passage between adjacent cells.