Substances necessary for normal growth and development of plants must continually be transported into cells while metabolic wastes must be eliminated so that they won’t accumulate inside the cells. For instance, water as well as mineral salts from the soil solution enter root cells while carbon dioxide and oxygen through tiny pores known as stomata in leaves and lenticels in stem. Excess oxygen not utilized during cell respiration as well as oxygen produced during photosynthesis is released to the atmosphere. In most cases, movement of these substances is along a concentration gradient, that is, from regions of greater concentration to regions of less concentration. Such type of transport is known as passive transport. Diffusion is a type of transport which is concerned with the movement of solute particles. Aside from concentration gradient, factors affecting the rate of diffusion include the temperature, size of diffusing molecules and presence of other molecules aside from the diffusing one. Osmosis, on the other hand, is another type of passive transport, which is involved in the movement of solvent (e.g. water) through a semi-permeable membrane. In osmosis, the presence of a differentially permeable membrane as well as differences in the concentration of the medium and the intracellular substance (i.e. cell sap) are factors to consider in determining the direction of water flow. (madel, dito gawa k ng visuals na puede,.. kung aong maisip mo di ko nga alam kung ano puede ndin ilgay …. Ano kaya gagamitin ntin? Naka-acetate oh sa manila paper kaw n bhala..;) Activity 4
Passive Transport in Plant Cells
To be able to:
1. Perform and observe the process of diffusion and osmosis. 2. give an operational definition of:
a. osmosis c. turgor pressure b. diffusion d. plasmolysis
3. list at least three practical applications for each.
Test tube Fresh specimens of: Glass rod sealed at one end lettuce leaf Cork slice of cucumber Potassium permanganate stem of celery Water beaker with strong saline solution
Dish of water B.
Leaf of Rhoeo discolor
.5 saline solution
.9 saline solution
1.5 saline solution
1. Fill a test tube with a solution of potassium permanganate 2. Fill a glass rod sealed at one end with water and invert it over the test tube with its open end just below the surface of the potassium permanganate solution. 3. Observe after 2 hours.
4. Answer guide questions listed after each part of the procedure has been done.
1. Strip off a thin layer of the outer epidermis of the undersurface of the leaf of Rhoeo discolor 2. Place a drop of distilled water on a microscope slide.
3. Add a cover glass and examine under the LPO, then HPO.
4. Focus on the stomata and observe the condition of the guard cells. 5. Apply a small piece of blotting or tissue paper on the edge of the cover slip to remove the water. 6. Place a drop of .5 saline solution on the slide, close to but not on the cover slip. 7. Draw the solution out under the cover slip by applying again a small piece of tissue paper to the opposite edge. 8. Examine under the HPO and observe the changes in the guard cells. 9. Repeat procedure number 6 to 8, but this time use the .9 saline solution; after which 1.5 saline solution follows. 10. Fill up the table on page 25.
a. Fig. 4.1...