1. Beaker A contains 100 ml of 5% salt solution and Beaker B contains 100 ml of
ID: 195112 • Letter: 1
Question
1. Beaker A contains 100 ml of 5% salt solution and Beaker B contains 100 ml of 2% salt solution. Which solution is hypertonic? 2. Which beaker has the greater amount of solute, salt? 3. If the solution in beaker A was placed in bag made up of a selective permeable membrane and placed in beaker B, what would happen? Explain. 4. Is this process active or passive? Explain. 5. If a potato plug was placed in beaker B and the cells underwent plasmolysis, what does this tell you about the salt content in the cytoplasm of the potato cells. Use the processes above to explain the following processes in plants. 6. During the daylight hours the guard cells cause the stomata to open in leaves and during the night the guard cells close the stomatal. 7. Region of elongation of roots the cells elongate (stretch). 8. The cells of tomato leaves are soft and flexible during a drought. 9. Movement of water from the soil to the xylem (vessel members) in the root by way of the symplast (last Wednesday'sExplanation / Answer
6) In day light, stomata open due to influx of water in guard cells. water enters into the guard cells due to decrease in water potential as a result of increase in solute concentration. Light activates two processes in guard cells:
7) Auxin produced in the shoot apex flows into the root through the central vascular tissue. in the columella region of root cap, the auxin flow is reversed and moves basipetally intp the cortical cells of the elongation zone, where it regulates cell elongation.
Auxin stimulates H+-ATPase proton pump, present on theplasma membrane. As a result, the pH of the membrane falls pH 4.5, activating a cell wall protein, expansin. Expansin disrupts the hydrogen bonding between the cellulose microfibrils, reducing the rigidity of the wall and thus the cell elongates.
9) Absorption of water by roots is a passive process. The movement of water through a cell membrane occurs as a result of two processes - diffusion and bulk flow.
Once the water is absorbed into the root hairs or epidermal cells, it must traverse the cortex to reach the xylem vessels. The path through which water move into xylem cells of roots occurs through both apoplast and symplast
Pressure-flow hypothesis - At the source, sugar is actively loaded into sieve element. Water enters the phloem cells osmotically, building up a high turgor pressure. At the sink, as sugars is unloaded, water exits the phloem cells and a lower pressure results.Water and its dissolved solutes moves by bulk flow from the area of high pressure (source) to the area of low pressure (sink).
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