Lesson Hook: "Magic Flowers"

Materials:

• 2 white Carnations
• Food colouring
• Jar
• Water

Procedure:

1. Pour water into the jar.
2. Add approximately 6 drops of food coloring into the jar.
3. Very carefully cut the stem on an angle and place it in the jar.
4. Let the flower stand in the water for24- 48 hours (2 days).
5. Record the colour of the flower every hour or so to see if there are any changes (you may also take pictures to get a better idea of the change).

Explanation:

This activity can be used as an introduction to the grade 11 Biology unit of plants. It represents how flowers absorb water through their stems. The xylem plays a big part in this process. The xylem is composed of thousands of tiny tubes, which each run from the roots to different parts of the plant. The roots act as a filter system and sorts what is taken up into the xylem and thus by cutting the roots, the filtering system is removed. This causes the flower to absorb whatever it is sitting in, including food colouring. The food colouring is taken up all the way into the leaves and petals, causing the flower to change colours. This occurs as water will travel from areas of high concentration to areas of low concentration. In this case the jar has the high water concentration and the area furthest from this; the petals have the lowest concentration.  Water is moved from the xylem into the cells by osmosis. Transpiration and cohesion are the processes that allow the water to move throughout the flower. Water evaporates from the stomata of the leaves and petals causing them to pulls water up from the stem of the plant (Marimore, 1998). This process by which water is lost is called transpiration. Water that evaporates from the leaves "pulls" other water behind it up to fill the space left by the evaporating water. This can happen because water sticks to itself (called water cohesion) and because the tubes in the xylem of the plant stem are very small.
 
Why This Hook is Worthwhile

This is a worthwhile activity to perform as an introduction to the plants units in grade 11 biology. Students are generally least enthusiastic about this unit and having them think and develop hypothesis about why this happens will help them become interested in the topic. They will also be able visually see the transport of water throughout the flower as the food colouring will slowly be moved into the flower petals. This will aid them in understanding the process of osmosis and making it more interesting.  

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Grade: 11 Biology, Academic SBI3U
Strand: Plants: Anatomy, growth and function.    
Specific Expectation: F3.1 describe the structures of the various types of tissues in vascular plants, and explain the mechanisms of transport involved in the  processes by which materials are distributed throughout a plant (e.g., transpiration, translocation, osmosis).