Guide to the practical teaching
of biology and genetics

Transport of substances, osmosis

TASK 1: Simple plasmolysis (plant cell in hypertonic solution)

NP: onion, 1 % neutral red; 1M KNO₃

Put the inner epidermis of an onion onto the slide and stain it with 1 % neutral red. Add 1M KNO₃ and observe the plasmolysis. Draw your observation and write a conclusion.

TASK 2: Deplasmolysis

Add distilled water to the specimen from the previous task and observe the reverse process (cytoplasm and vacuoles increase their volume). Some cells are irreversibly damaged.

Fig.: Osmosis in epidermis of onion – simple plasmolysis

TASK 3: Spasm plasmolysis (plant cell in hypertonic solution)

NP: onion, 1 % neutral red; 1 % CaCl₂, 1M KNO₃

Stain the epidermis of an onion with 1 % of neutral red; add 1 % CaCl₂ and 1M KNO₃. Observe the unequal separation of the cytoplasmic membrane from the cell wall caused by the increased cohesion of cytoplasmic membrane.

Fig.: Osmosis in epidermis of onion – spasm plasmolysis

TASK 4: Turgor (plant cell in hypotonic solution)

NP: pollen grains, H₂O

Put pollen grains on the slide and observe them using microscope. Then add water, cover with a cover glass and observe again. Write your observation.

Fig.: Osmosis: A – pollen grain in isotonic solution, B – pollen grain in hypotonic solution.

TASK 5: Macroscopic observation of osmotic haemolysis (blood in hypotonic solution)

NP: blood, H₂O, physiological solution

Take two tubes and add 1 ml of blood into each of them. Then add 3 ml of physiological solution into one of them and 3 ml of water into the second one. Gently mix and compare both tubes. Perform the "reading test". Write down the result of your observation.

TASK 6: Microscopic observation of osmotic haemolysis

NP: blood, H₂O

Put a small drop of blood on the slide and cover with a cover glass. Add water to one edge of the cover glass and let it suck in the part of the specimen. Then immediately suck the water off using a filter paper. Water causes haemolysis (rupture of erythrocytes) observed on interface of water and blood.

TASK 7: Plasmorhisis (animal cell in hypertonic solution)

NP: blood, KNO₃

Put a drop of blood on the slide, add 1M KNO₃ and cover with a cover glass. You can observe shrunk erythrocytes (star-shaped) because of water escaping from them. Draw them and write a conclusion.

Fig.: Osmosis. A – haemolysis of erythrocytes, B – plasmorhisis of erythrocytes.

TASK 8: Phagocytosis

PP: phagocyting leucocytes stained by Pappenheim method

Find and draw leucocytes with phagocyted particles. You can count phagocytic activity (PA): PA = number of phagocytic cells / total number of cells.

Fig.: Leucocytes with phagocyted particles.