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As a result, water moves from the phloem by osmosis and is then transpired or recycled via the xylem back into the phloem sap. Figure 4.5.2.4 4.5.2. 4: The pressure-flow hypothesis of assimilate transport. The assimilate, which is rich in sucrose, is actively transported from source cells into companion cells and then into the sieve-tube ...
- 4.5.3: Chapter Summary
Water potential and transpiration influence how water is...
- 4.5.3: Chapter Summary
Oct 26, 2023 · The function of phloem tissue in a plant is to: Transport organic compounds (assimilates), particularly sucrose, from the source (e.g. leaf) to the sink (e.g. roots). The transport of these compounds in phloem tissue can occur up and down the plant. The organic compounds are dissolved in water to form sap. Phloem is a complex tissue made up of ...
9.2 U 3 Active transport is used to load organic compounds into phloem sieve tubes at the source. State that sucrose is the most prevalent solute in phloem sap. Outline why sucrose is used for phloem transport, as opposed to glucose. Describe the active transport of sucrose into the phloem via a co-transport protein.
Oct 31, 2023 · Phloem sap travels through perforations called sieve tube plates. Neighboring companion cells carry out metabolic functions for the sieve-tube elements and provide them with energy. Lateral sieve areas connect the sieve-tube elements to the companion cells. Once in the phloem, the photosynthates are translocated to the closest sink.
The sieve tubes absorb water from the surrounding xylem and develop a high turgor pressure (Fig. 11.43). It causes the flow of organic solution towards the area of low turgor pressure. A low turgor pressure is maintained in the sink region by converting soluble organic substances into insoluble form.
May 8, 2023 · The mass flow of organic solutes within the phloem tissue occurs above and below the sources (which is typically photosynthesising leaves). Therefore sap flows upwards and downwards within a plant. The translocation of phloem sap (sucrose and other organic solutes) due to a hydrostatic pressure gradient from the source to the sink.
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Sucrose produced in the Calvin cycle is loaded into the sieve-tube elements of the phloem, and the increased solute concentration causes water to move by osmosis from the xylem into the phloem. Information presented and the examples highlighted in the section support concepts outlined in Big Idea 2 and Big Idea 4 of the AP ® Biology Curriculum Framework.
