Bio 11 – Botany – Exercise 11 – Plant Water Relations

A. Diffusion

1. Steam for 10 seconds three 0.5 cm cubes of yam roots resting on a wire mesh or strainer. Place this in a mesh or strainer. Place this in a 500-mL beaker 3/4 filled with watr. Prepare a similar set-up using unsteamed cubes. leave both set-ups undisturbed and observe after 30 mintues and at the end of the laboratory period.

1.1 Compare the color intensities in different parts of the beakers at the start of the experiment and after each observation.

Steamed yam roots – red color more intense

1.2 How do the two treatments compare in the rate of spread of the color?

Steamed yam roots – faster

1.3 How would you account for the difference?

Increase in temperature leads to increase in kinetic energy, which leads to an increase in rate of diffusion.

B. Osmosis

3. Put into 8 small test tubes 10 ml of each of the following sucrose solutions: 5 %, 10%, 15%, and 20%. With a scalpel and a pair of forceps carefully peel off uniform small strips of the lower epidermis of leaves o boat of Moses. Examine the strip of the epidermal tissue to verify that it consists of intact cells containing the violet-colored anthocyanin pigments. Drop a strip into each test tube, at about 5-minutes intervals between successive tubes. After a 30-minute immersion of each strip, examine the cells under the microscope, mounting the strip in the same solution in which it has been immersed. Examine one microscope field underLPO and count the number of plasmolyzed cells as indicated by the shrinkage of the cytoplasm.

3.1 What is plasmolysis?

Loss of water from the cell within plants by osmosis

4. Prepare another section of the lower epidermis of boat of Moses. Examine the section under the LPO and select a thinner portion where the stomata are clearly seen, wide open and free from dirt and foreign matter. Focus on one cell with the widest stoma under HPO.

4.4 Explain the effect of sugar solution on the changes in pore size.

Sugar solution is hypotonic. In a hypotonic solution, cells are plasmolyzed. The guard cells sag, inner cell walls come closer and so the stoma closes.

Notes:

Data for Table 11.1 (under Osmosis) is different for each group and class. You’ll need data from your class. The sketch for 3.4 *under Osmosis) is pretty easy – just like how your instructor/ lecture professor drew it. The sketches for 4.1 and 4.3 (under Osmosis) are like how your instructor drew them.

No answer for”4.5 What factors and structures in the guard cells are responsible for the opening and closing of the stomata”. Just expound on answer for 4.4