Water Movement in Plants

Materials

2 stalks of fresh celery (one with the leaves on)

1 carrot

red and green food coloring

scalpel

2 200 mL beakers

millimeter ruler

Procedure

Part A - Water Movement in Stems

1. Using a scalpel, remove approximately 1 cm from the bottom of two celery stalks. Remove the leaves from one of the celery stalks.

2. Pour approximately 100 mL of water into a 200 mL beaker and add five drops of red food color. Immerse both celery stalks in the solution for 30 minutes and proceed to Part II of the lab.

a) Predict which celery stalk will show the greatest movement of dye up the stalk. Provide a reason for your prediction.

3. After the 30 minutes, place both celery stalks on paper towels and, using the scalpel, make three cuts in each at 1 cm intervals, starting 1 cm from the bottom of the stalks.

b) What evidence suggests that the dye has moved up the stalk?

4. Continue cutting the celery stalk until the dye can no longer be seen in the xylem vessels.

c) Using a ruler, measure the distance in millimeters the dye has moved in each stalk. Record your measurement.

Part B - Water Movement in Roots

5. Cut off 2 cm from the lower end and 1 cm from the top of the carrot.

6. Put the lower end into a 200 mL beaker that contains 2 cm of water that has been strongly coloured with green or blue food colouring. Set the beaker and carrot aside for 24 h.

7. Observe the carrot and record any changes that have occurred.

8. Cut off 1 cm from the lower end and observe the cross section. Repeat at the upper end of the carrot. Compare the two cross sections and record your observations.

9. Choose a deeply stained region and cut a very thin cross section with a razor blade. Prepare a wet mount. Observe the stained cells in the microscope and describe their structure. Make a drawing of the cross section, showing all areas that took up the food colouring.

10. Use the razor blade to cut the rest of the carrot lengthwise through its core. Note the location of the stained cells.

Questions

1. Explain how water moves up the stems of plants? (cohesion of water molecules, evaporation from theleaves, to a limited extent, root pressure)

2. What evidence is there that dye had moved into the leaves? (should see dye in the xylem)

3. From your results, what can you say about the role of leaves in transpiration? (leaves are the site oftranspiration)

4. For what does the plant need the water absorbed by the roots? (photosynthesis and turgor pressure)

5. a) What region of the carrot absorbed the coloured water? (central core)

b) What type of tissue is found there? (xylem)

c) What is the usual function of tissue in this area? (conduct water upward)