A LABORATORY PROTOCOL ON THE BIOLOGY EXPERIMENT CARRIED OUT BY PORTUGAL

EXPERIMENTAL PROTOCOL 

Investigating the upward transport of xylem sap 

Introduction 

The xylem is the vascular tissue responsible for the upward conduction of water and mineral ions from the roots. Xylem sap (mainly water and mineral ions) circulate through specialized tissues – conductive vessels – from the root, through the stem, to the leaves, fruits and flowers, regardless of the inclination of the branches, generally counteracting the force of gravity. 

Objective 

Check the ascent of the xylem sap, along the stem, to the flowers, against the force of gravity. 

Materials used: 

• 2 white flowers (e.g. carnations); 

• 2 X 250 ml Erlenmeyer flasks; 

• Vital dye (methylene blue, neutral red) or a food coloring; 

• Water; 

• Forceps and scalpel; 

• Acetate marker; 

• Binocular magnifying glass 

Process: 

1. Place 200 ml of tap water or mineral water in each Erlenmeyer flask. 

2. Put a few drops of dye in one of them, until the solution is visibly colored. 

3. Cut the end of each of the flowers petioles; immediately place each one of them in one of the Erlenmeyer flasks. 

4. Mark the water level of the Erlenmeyer flasks with the aid of an acetate marker. 

5. Leave the assembly in a ventilated and well-lit place. 

6. Observe daily – color of leaves and flowers and water level. 

7. When the color of the dye on the leaves/flowers becomes visible, remove them from the water and cut a cross section of the petiole, a little away from the final region. 

8. Observe with the magnifying glass. 

9. Record observations using a photo or diagram. 

Results: 

(Photograph of the flower colored with the color of the dye; water levels; diagramo of the stem cross section) 

Discussion of results 

1. What hypothesis would be suitable for this protocol? 

2. Which is the control group? 

3. How is the bluish tone of the flowers explained? 

Conclusions: 

(The results confirm the hypothesis).