Experiment No. 1 Date: __________
Aim: To study by demonstrating the osmosis process by potato osmoscope.
Principle: Molecules of solvent move from its higher concentration to lower concentration. It can pass through a selectively permeable membrane like the plasma membrane of cells (osmosis).
Materials Required: A potato tuber, 20% sugar solution, beaker, water, stain, scalpel, two pins of different colours.
Procedure:
- Slice the potato tuber into two equal halves and then into cubes with the help of a scalpel.
- From the mid-region of the tuber, scoop from the soft parenchyma, so as to form a tiny cavity of a cube shape. At the base, the cavity prepared should have a minimum thickness.
- Fill up half the cavity with the freshly prepared 20% sugar solution. Into the cavity, fix a pin in a way that the mark is in the same line with the layer of the sugar solution.
- Set up the osmoscope in a beaker that is filled with water in a way such that 75% of the potato osmoscope is immersed in water. Add several drops of stain to colour the water of beaker.
- The set up should remain uninterrupted for close to 1 hour.
- Notice the sugar solution in the osmoscope towards the end of the experiment. The sugar level rises. Fix another pin to mark the level.
Observation:
After a period of time, within the osmoscope, the sugar solution rises and is seen coloured.
Conclusion:
- An increase in the level of sugar solution is observed in the osmoscope. It is because of the entrance of water due to endosmosis from the beaker.
- Also, a water potential gradient is built between the sugar solution in the external water and the osmoscope.
- Though both the liquids are divided by living cells of the potato tuber, they allow the entrance of water into the sugar solution.
- This demonstrates the entrance of water into the sugar solution through the tissues of potato serving as a selectively permeable membrane.
- Experiment No. 2 Date:
__________
Aim: To demonstrate endosmosis in raisins and find the percentage of water absorption.
Principle: Water moves from its higher concentration to lower concentration. It can pass through a selectively permeable membrane like the plasma membrane of cells (osmosis).
Materials Required: A few raisins, digital weighing scale, beaker, water, blotting paper.
Procedure:
1. Take three or four raisins and weigh it on a digital weighing scale. Note the weight W1.
2. Soak them by putting them in a beaker filled with pure water.
3. After two hours, take out the raisins and wipe them dry using a blotting paper.
4. Weigh the raisins on the digital weighing scale. Note the weight W2.
Observation:
After a period of time, the raisins absorb water and get swollen because of endosmosis.
Initial weight of raisins = W1 = _________
Weight of swollen raisins = W2 = _________
Weight of absorbed water = W3 = W2 – W1 = __________
Percentage of water absorbed by raisins = (W3/W1) x 100 = ________ %
Result:
Raisins exhibit endosmosis and absorb water when soaked in it.
The percentage of water absorption of the given sample of raisin = _______%
Experiment No. 3 Date: __________
Aim: To demonstrate unequal transpiration by four-leaf method.
Principle: Transpiration takes place through stomata of leaves. If petroleum jelly is applied on leaves, water vapour is not able to escape.
Materials Required: Four equal-sized fresh leaves of Hibiscus plant, petroleum jelly, string, stands and soft cloth
Procedure:
1. Take four equal-sized fresh leaves of Hibiscus plant along with their petiole. Let us name them A, B, C and D.
2. Place them on the working table. Clean the leaves carefully with a soft cloth.
3. On leaf A, apply petroleum jelly on both the surfaces – upper and lower surfaces.
4. On leaf B, apply petroleum jelly on the lower surface only.
5. On leaf C, apply petroleum jelly on the upper surface only.
6. On leaf D, do not apply petroleum jelly on any surface.
7. Tie the leaves to a string from their petioles. Arrange the leaves in a proper order. A label tag can be tied along with each leaf.
8. Tie the string between two stands so that the leaves remain hanging; and leave the set-up to dry in sunlight for about two or three hours.
Observation:
After two or three hours, it is seen that the leaves wilt but to different degrees.
1. Leaf A shows no sign of wilting.
2. Leaf B shows slight wilting. The leaf bends towards the dry surface i.e. the upper surface.
3. Leaf C shows significant wilting. The leaf bends towards the dry surface i.e. the lower surface.
4. Leaf D shows the highest dryness and wilting.
Conclusion:
1. Transpiration is unequal on the upper and the lower surfaces of a dicot leaf.
2. Stomatal distribution on the lower surface of dicot leaves is significantly higher than on the upper surface.
Experiment No. 4 Date: __________
Aim: To demonstrate transpiration through bell-jar experiment.
Principle: Transpiration is the release and evaporation of water from the surface of leaves through stomata. The phenomenon of transpiration can be demonstrated by bell-jar experiment.
Materials Required: Bell jar, well watered potted plant, plastic sheet, petroleum jelly, porcelain tile
Procedure:
- Take a well watered potted plant and cover it with a plastic sheet. The aerial parts of the plant should be left uncovered.
- Place the plant on the porcelain tile and cover it with a bell jar.
- Seal the gap between the bell jar and the tile with some petroleum jelly to make it air tight.
- Prepare a same setup but without a plant in the second bell jar.
- Place the apparatus in sunlight for some time.
Observation: Water drops appear inside the walls of the bell jar containing potted plant whereas no water drops appear in the bell jar without a plant.
Conclusion: Water is evaporated from the surface of leaves through transpiration in presence of sunlight.
Experiment No. 5 Date: __________
Aim: To study plant growth by using arc auxanometer.
Principle: Growth in a plant takes place mainly in the apex of the plant. If the apex of the plant is tied to a string and arranged in an arc auxanometer, the growth of the plant can be measured.
Materials required: Arc auxanometer, a growing potted plant, string, weight, scale, water
Procedure:
1. Take an arc auxanometer and measure the radius of its pulley and the length of the pointer. Note the readings.
2. Take a growing potted plant and water it.
3. Take a strong string and tie one end of the string to the apex of the potted plant.
4. Pass the string over the pulley of the arc auxanometer and on the other end of the string tie a suitable weight.
5. Set the pointer on the arc to zero or note the initial reading.
6. Allow enough sunlight or light to fall on the plant.
7. After 24 hours note the reading of the pointer on the arc.
Observation:
1. Radius of the pulley= 1 cm
2. Length of the pointer = 10 cm
3. Initial reading of the pointer = 1 cm
4. After 24 hours, final reading of the pointer = 9 cm
5. Difference = 9—1 = 8 cm
Result:
Actual growth of the plant = Distance travelled by the pointer x Radius of the pulley
Length of the pointer
= 8 x 1 cm
10
= 0.8 cm
Experiment No. 6 Date: __________
Aim:
To show experimentally that carbon dioxide is released during respiration.
Materials Required:
Respiroscope, stand, some germinating seeds, a beaker, KOH solution
Procedure:
1. Take some germinating seeds and soak them in water.
2. Fill them in the bulb of a respiroscope.
3. Fix the respiroscope on a stand.
4. Take a beaker and fill it with KOH solution.
5. Dip one end (tube) of the respiroscope in the beaker filled with KOH solution. Note the level of solution in the tube.
6. Plug the cork on the bulb. The respiroscope must be air tight.
7. Keep the set up undisturbed for about 30 minutes.
8. Observe the rise of solution in the tube.
Observation:
KOH solution rises up in the tube of the respiroscope.
Conclusion:
The rise in the level of KOH solution indicates that CO2 is produced by germinating seeds during respiration. Actually, the germinating seeds respire and produce CO2, which is absorbed by KOH solution. This creates a vacuum in the respiroscope and its tube. The air present in the tube moves into the bulb. This pulls the KOH solution upwards.
Thus, carbon dioxide is released during respiration.
Experiment No. 7 Date: __________
Aim: To prove that oxygen is produced during photosynthesis
Principle: Aquatic plants grow in water. The oxygen they release while photosynthesis can be collected in an inverted test tube.
Materials Required: An aquatic plant, a beaker, funnel, test tube, water
Procedure:
1. Place an aquatic plant in a beaker containing water.
2. Cover the plant with a funnel.
3. Invert the test tube full of water and cover the stem of the funnel.
4. While placing the test tube, ensure that the level of the water in beaker is above the level of stem of funnel.
5. Expose the apparatus to the sunlight.
6. After few hours, gas bubbles will form and collect in the test tube.
7. Test the gas in the test tube.
8. A glowing splinter (piece) bursts into the flame shows the presence of oxygen.
Observation: Gas bubbles in a test tube and gets collected in it. This gas promotes combustion by brightening the flame.
Result: The gas collected in the test tube is oxygen.
Conclusion: Formation of gas bubbles prove that oxygen is produced by the green plants during photosynthesis.Experiment No. 8 Date: ___________
Aim: To demonstrate through Moll’s experiment that CO2 is necessary for photosynthesis
Materials Required: A potted plant, caustic potash (KOH) solution, a flask, split cork, iodine solution, water, alcohol, petridish
Procedure:
1. De-starch a potted plant by putting it in complete darkness for two days.
2. Fill partly a flask with strong solution of caustic potash and fit a split cork on its mouth.
3. Insert about half of the portion of a leaf of the de-starched plant into the flask through the split cork.
4. Apply grease on the upper portion of split cork to make it air tight.
5. Water the plant and leave the apparatus in bright sun light for several hours.
6. Later, pluck the whole leaf and boil it in a solution of alcohol and water for some time.
7. Take the leaf and keep it in a petridish.
8. Put a few drops of iodine solution on the whole leaf.
Observations:
Portions of the leaf inside the flask as well as in between the split cork show negative test for starch indicating the absence of photosynthesis while the portions outside the split cork show positive test for starch indicating the presence of process of photosynthesis in this region.
Results:
Negative starch test by the leaf portion present inside the flask and positive test of starch shown by the portions of the leaf present outside the flask proves that CO2 is necessary for photosynthesis.
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