Part 4: Water and assimilate movement
1. Introduction
Assimilate = a substance that the plant takes up or accumulates
Translocation = the movement of assimilates around a plant
Xylem = tissues which transfer water and minerals throughout the plant from the roots
Phloem = tubes within stems, leaves and roots that translocate the assimilates
Assimilates, produced or taken up by a plant, are moved around the plant in a process called translocation.
Assimilate are moved from source (where they are made or taken into the plant) to sink (where they are needed, for example a developing flower).
Assimilates can be used to make substances that the plant requires immediately, or they can be stored.
Nutrients are translocated from source (where they are taken into the plant or made in the plant) to sink (where they are used by the plant).
The vascular bundles (made up of xylem and phloem tissues) reach throughout the plant and so are used by the plant to send signals. You can imagine them as bundles of straws winding their way through the roots, stems and leaves. The signals sent through these tubes can be in the form of plant hormones or they can be turgor (water pressure) or electrical signals.
Example: Roots signal drought stress to leaves by releasing abscisic acid into the vascular bundles so that stomata can be closed, and water loss reduced.