How to see photosynthesis in action using spinach leaves

Photosynthesis is one of the most interesting processes in nature. In this experiment, this process can be observed by following the movement of spinach leaf disks in a sodium bicarbonate solution.

How photosynthesis occurs

Photosynthesis is the process in which plants transform light energy into chemical energy. With sunlight, water, and carbon dioxide (CO ₂ ), glucose and other sugars are produced, and oxygen (O) is released. This process allows plants and other autotrophic organisms to produce their own food.

Spinach characteristics

Like other plants, spinach, Spinacia oleracea , photosynthesizes and is characterized by its large, dark green leaves.

It is part of the basis of healthy eating and can be eaten fresh or cooked. It is characterized by being very nutritious, since it contains vitamins A, E and K, and antioxidants. Like most leafy vegetables, it has a large amount of water and is low in protein, carbohydrates and fat.

In order to understand this complex process and easily see the results of the experiment, we will carry out the demonstration with discs of spinach leaves.

To do this, we will place them in a solution of water and baking soda. By obtaining carbon dioxide from these two elements, the leaf disks will sink into the container.

When exposed to sunlight, they will use carbon dioxide and water to produce oxygen and glucose. In this way, the oxygen that is released through them will form small bubbles and the leaves will begin to float.

Photosynthesis experiment with spinach leaves

In order to carry out the following demonstration of photosynthesis in this experiment, some materials are needed that are very easy to find in any home:

Materials

• 2 fresh spinach leaves
• Sodium bicarbonate (NaHCO₃)
• Water
• Liquid dishwashing detergent
• Plastic syringe 10 cc or larger, without needle
• 2 transparent containers
• 1 cup or glass
• Sunlight or large lamp
• Paper hole punch

Preparation

• With the hole punch make 20 holes in the spinach leaves, avoiding the edges of the leaves or the ribs. It is recommended to use smooth and thin leaves, which are not fleshy or have large veins.
• First, fill one of the transparent containers with approximately 100 ml of water. Then add half a teaspoon of baking soda and a drop of detergent.
• Withdraw the plunger from the syringe and put 10 spinach leaf disks into it. Replace the plunger and push it in until there is the least amount of air without crushing the discs. Then fill the syringe halfway with the sodium bicarbonate solution. Then plug the hole and pull the plunger several times to remove any oxygen from the discs. Repeat a few times until the disks stop floating and are at the bottom of the syringe.
• If the discs do not sink, new discs and a higher concentration of baking soda with a little more detergent should be used.
• Subsequently, place the discs of spinach leaves in the transparent container that has the solution of baking soda and detergent. All discs should sink to the bottom of the container.
• Expose the container to sunlight or a bright lamp. As the leaves produce oxygen, bubbles that form on the surface of the discs will move them and they will rise to the surface. If the light source is removed, the discs will sink again.
• To check the effect of the photosynthesis process you can experiment with light intensity, duration of exposure, and bicarbonate concentrations.

The chemistry behind this experiment

In nature, through the stomata or pores of the plants, they absorb carbon dioxide (CO ₂ ), water and the nutrients they need to carry out photosynthesis. Through chloroplasts, photosensitive cells, that is, they react to light, plants can capture light energy and convert it into chemical energy.

In the experiment, by adding the baking soda and water and receiving the light energy from the sun or lamp, the plant cells start photosynthesis and release oxygen. In the container, the oxygen forms the air bubbles and allows the small discs of spinach leaves to float to the top.

Bibliography

• Faverón Patriu, OE The mysteries of plants and fungi: plants, mosses, fungi. (2021, Kindle Edition). Spain. Oswaldo Enrique Faverón Patriu.
• Freeman, S. Fundamentals of Biology . (2018). Spain. pearson.
• Tompkins, P.; Bird, C. The secret life of plants. (2016). Spain. Captain Swing.
• Zúñiga González, Andrés Camilo. 2020, April 2. Experiments on photosynthesis. DIY Science . Available at: https://www.youtube.com/watch?v=Esrw5Znvhrc