PHOTOSYNTHESIS LAB: Floating Leaf Disks: AP Biology

Summary

In this Madden Science video, we delve into the floating leaf disk assay, a lab experiment exploring factors affecting photosynthesis rates in leaves. The lab is a favorite for its simplicity, affordability, and adaptability. Key variables include light intensity, temperature, and sodium bicarbonate levels. Using a syringe to submerge leaf disks in a carbon dioxide-rich solution, students observe how oxygen production causes the disks to float. The video introduces a pocket lab to measure light intensity, a crucial factor in photosynthesis, and encourages viewers to explore other variables in part two of the experiment.

Takeaways

• 🌿 **Lab Introduction**: The video introduces a lab on photosynthesis, specifically the floating leaf disk assay, which is part of the energetics unit in AP Biology.
• 🔍 **Objective**: The main goal is to explore the factors affecting the rate of photosynthesis in living leaves, focusing on rates and variables.
• 🧪 **Materials Needed**: Key materials include a syringe, baking soda solution, a hole punch, a light source, and a heat sink.
• 🍃 **Leaf Selection**: The lab uses the hardest leaves available, punched to create discs that are then filled with a solution to sink them.
• 💧 **Baking Soda Solution**: Baking soda provides a carbon source for the leaves during photosynthesis, replacing air with carbon dioxide-rich water.
• 🌞 **Light as a Variable**: Light intensity is a key environmental variable that can be manipulated by changing the distance or color of the light source.
• 🌡️ **Temperature Consideration**: Heat can affect the experiment, so a heat sink or cover can be used to regulate temperature.
• 📊 **Data Analysis**: The lab involves observing how many leaf discs float over time, with a focus on the time it takes for half of the discs to float (estimated time 50).
• 📉 **Environmental Variables**: Factors like light intensity, temperature, and pH are considered environmental variables that can affect photosynthesis.
• 🔬 **Pocket Lab Usage**: A pocket lab device is used to measure light intensity, providing precise data to correlate with the rate of photosynthesis.
• 🌐 **Adaptability**: The lab is noted for its adaptability, allowing for various experiments to be conducted with different variables.

Q & A

What is the main focus of the 'Madden Science' video?

The main focus of the 'Madden Science' video is exploring photosynthesis, specifically the factors that affect the rate of photosynthesis in living leaves.

What is the name of the lab experiment discussed in the video?

The lab experiment discussed in the video is often called the 'floating leaf disk assay'.

What are the two main things the lab is investigating?

The lab is investigating rates and factors that affect the rate of photosynthesis.

What is the purpose of using baking soda solution in the lab?

The baking soda solution provides a carbon source for the leaves when they undergo photosynthesis.

Why do the leaves float initially in the experiment?

The leaves float initially because the spongy mesophyll layer inside the leaf is filled with air.

How does the experiment increase the density of the leaf disks to make them sink?

The experiment increases the density of the leaf disks by replacing the air in the mesophyll layer with water that contains carbon dioxide from the sodium bicarbonate solution.

What happens when the leaf disks are placed under the light source?

When the leaf disks are placed under the light source, photosynthesis occurs, producing carbohydrates and oxygen, which causes the disks to float due to decreased density.

How is the rate of photosynthesis measured in the lab?

The rate of photosynthesis is measured by observing how quickly the leaf disks start to float after being placed under the light source.

What is the 'estimated time 50' mentioned in the video?

The 'estimated time 50' refers to the time it takes for half of the leaf disks (five out of ten) to start floating, indicating the rate of photosynthesis.

What are the three groups of variables that can affect the rate of photosynthesis?

The three groups of variables that can affect the rate of photosynthesis are environmental variables, plant or leaf variables, and method variables.

How can light intensity be adjusted in the experiment?

Light intensity can be adjusted in the experiment by changing the distance of the light source or by changing the light color.

What role does the Pocket Lab Voyager play in the experiment?

The Pocket Lab Voyager is used to measure light intensity, providing precise data on how much sunlight or energy is being fed into the photosynthesis process.