Equipment
Method
Results
- red onion
- six different NaCl solutions. For this experiment; 0.1,0.2,0.3,0.4,0.5,0.6 moldm^-3
- distilled water
- six 5cm^3 syringes
- pipettes
- scalpel
- pen
- microscope
- forceps
- slides, coverslips
Method
- Carefully cut small sections of the red onion epidermis, so that they are only one cell thick.
- Using the pipette put the 6 different solutions onto labelled watch glasses.
- Use the forceps to transfer a section of the epidermis into each watch glass, making sure that the epidermis is fully submerged.
- Leave in the solutions for 20 minutes.
- Prepare 6 slides by putting a drop of the corresponding solution onto each slide, labelling what solution it is.
- Using the forceps, after 20 minutes transfer the epidermis onto the slide with the corresponding solution.
- Place a coverslip on the slide and view under a microscope.
- Observe 25 cells and record how many are plasmolysed. Use a suitable table to show results.
Results
Conclusion
The results clearly show that as the concentration of NaCl increases the greater the proportion of cells are plasmolysed. This is because the water potential of the solution decreases, therefore more water moves out of the onion cells, which increases the proportion of cells plasmolysed. When 50% of the cells are plasmolysed, it is called incipient plasmolysis, as the concentration inside the cells is equal to the concentration outside of the cell. On my graph this lies between 0.3 and 0.4 moldm-3, it lies closer to 0.4 so I would estimate the value for the incipient plasmolysis is 0.36 moldm-3.
The results clearly show that as the concentration of NaCl increases the greater the proportion of cells are plasmolysed. This is because the water potential of the solution decreases, therefore more water moves out of the onion cells, which increases the proportion of cells plasmolysed. When 50% of the cells are plasmolysed, it is called incipient plasmolysis, as the concentration inside the cells is equal to the concentration outside of the cell. On my graph this lies between 0.3 and 0.4 moldm-3, it lies closer to 0.4 so I would estimate the value for the incipient plasmolysis is 0.36 moldm-3.