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The plasmodesmata allow the direct flow of small molecules such as sugars, amino acids, and ions between cells. Larger molecules, including transcription factors and plant viruses, can also be transported through with the help of actin structures.
This allows direct cytoplasm-to-cytoplasm flow of water and other nutrients along concentration gradients. In particular, symplastic flow is used in the root systems to bring in nutrients from soil. It moves these solutes from epidermis cells through the cortex into the endodermis. Once solutes reach the endodermal cells thorough apoplastic flow, they are forced into the symplastic pathway due to the presence of the Casparian strip. Once the solutes are passively filter ed, they eventually reach the pericycle, where it can be moved into the xylem for long distance transport. It is contrasted with the apoplastic flow, which uses cell wall transport.
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