Hint: They are the transport channels of the membrane that cross the walls of plant cells. These are the connecting link between the plasma membranes, cytoplasm, and endoplasmic reticulum of cells and helps in the transportation of various macromolecules in between them. Plasmodesmata enables transportation and communication between the cells.
Plasmodesmata are connections between adjacent cells that are microscopic channels evolved in several lineages and have structures that include members of Phaeophyceae, Coleochaetales, etc. The polysaccharide cell wall surrounds the cell while the cell wall separates the neighboring cells are separated by a pair of cell walls. In between the layers, the middle lamella forms the apoplast. Plasmodesmata only allow those substances that are permitted by the cell wall and are small. Plasmodesmata are of two forms i.e. primary plasmodesmata which are formed during cell division and secondary plasmodesmata which are formed between mature cells. They allow the molecules to pass through the cell gaps of the plant cells by the symplastic pathway while in animal cells the various membranes and the gap junction interconnect. Around 1000 – 100000 plasmodesmata are found in a plant cell that connects with the adjacent cells. They are 50-60 nanometres in India diameter and are constructed of three main layers i.e. cytoplasmic sleeve, plasma membrane, and the desmotubule.
The endoplasmic reticulum forms the primary plasmodesmata and is located across the middle lamella. Between the two newly divided plant cells a new cell wall is synthesized. These wales as the cytoplasmic connections present between the cell and their cell walls. The fall of the plasmodesmata is not thick and depresses Earth in areas which are known as pits formed in the walls. It transports proteins, messenger RNA, viroids, viral genomes, and short interfering RNA. They are used by cells in phloem and symplastic transport which is used to regulate sieve tubes by companion cells. Plasmodesmata causes negative effects like the spread of viruses. It consists of myosin proteins, actin microfilaments, and microtubules. The viral movement proteins to plasmodesmata are transported by actin microfilaments which allow for Cell cell transport while the viral charges are transported through myosin into the plasmodesmata and the viral RNA is transported through microtubules.
So, the correct answer is 'Connection between two adjacent cells'.
Note: Plasmodesmata impacts on auxin-induced phototropism and lateral root initiation. Plasmodesmata were discovered by Edward Tang in the higher plants in the late 1880s. Later it was found that it is present in all green plants. The origin of plasmodesmata in the endoplasmic reticulum. They are dynamic channels. They are the holes in the cell wall between the cells and allow them to be interconnected.