Hydrilla Experiment – Reveals the Release of Oxygen during Photosynthesis

Hydrilla Experiment - plant nutrition

Photosynthesis is a fundamental process that allows plants to use sunlight and convert it into chemical energy. It plays a crucial role in sustaining life on Earth by producing oxygen and forming the basis of the food chain. To better understand the intricacies of photosynthesis, scientists often conduct experiments. One such experiment uses Hydrilla, an aquatic plant, to demonstrate the evolution of oxygen during photosynthesis. In this article, we will explore the procedure, observations and significance of the Hydrilla experiment to shed light on the fascinating process of photosynthesis.

Background Information

Hydrilla (Hydrilla verticillata) is an aquatic plant commonly found in freshwater ecosystems. It has several unique adaptations that allow it to thrive in aquatic habitats. Hydrilla has finely divided, twisted leaves that maximise its surface area for efficient absorption of light and nutrients. It also has small air spaces in its leaves, stems and roots that allow it to swim and exchange gases.

Photosynthesis is the process by which green plants, algae and some bacteria convert light energy into chemical energy that is stored as glucose. This energy conversion is facilitated by a pigment called chlorophyll, which is found in the chloroplasts of plant cells. During photosynthesis, plants absorb light energy, use carbon dioxide from the atmosphere and extract hydrogen from water to synthesise glucose molecules. Oxygen is released as a by-product.

Experiment Procedure

To conduct the Hydrilla experiment, you will need the following materials- a transparent beaker or glass jar, a healthy Hydrilla leaf, a light source (e.g. a lamp or sunlight), a carbon dioxide source (baking soda and water solution) and a heat source (optional).

Set up the experimental apparatus

  • Fill a beaker or glass with water so that the Hydrilla leaf is completely submerged.
  • Dissolve a small amount of baking soda in the water to create a source of carbon dioxide. This helps to mimic the natural conditions necessary for photosynthesis.
  • Place the cup/jar near a light source so that the Hydrilla leaf receives sufficient light.

Collect and prepare the Hydrilla leaves-

  • Select a healthy, vibrant Hydrilla leaf.
  • Rinse the leaf gently under running water to remove dirt and impurities.
  • Cut the stem of the leaf at an angle to create a fresh opening for water to enter.

Expose the Hydrilla leaf to light

  • Submerge the prepared Hydrilla leaf in the beaker filled with water, making sure that the leaf remains completely submerged.
  • Position the beaker/jar in a way that allows the Hydrilla leaf receives sufficient light from the light source.

Hydrilla Plant Experiment Diagram

Hydrilla Experiment - Reveals the Release of Oxygen during Photosynthesis
Hydrilla Experiment diagram

Observation of oxygen bubbles

  • Observe the Hydrilla leaf over a period of time and note any changes.
  • When photosynthesis takes place, you will observe that small bubbles form on the surface of the hydrilla leaf.
  • Note the rate and frequency of bubble formation.

Observations and Results

  • During the experiment you will make the following observations-
  • When the Hydrilla leaf is exposed to light, small bubbles begin to form on the surface.
  • Over time, the speed and frequency of bubble formation increase.
  • The bubbles consist of oxygen, which is a by-product of photosynthesis.
  • These observations indicate that the Hydrilla leaf is undergoing photosynthesis and releasing oxygen in the process. The presence of oxygen bubbles is tangible and observable evidence of this important biological process.


The Hydrilla experiment provides a hands-on opportunity to witness the process of photosynthesis in action. When the Hydrilla leaf is exposed to light, it absorbs light energy through its chlorophyll pigments, which are found in the chloroplasts of its cells. The absorbed light energy is then used to convert carbon dioxide and water into glucose (a form of sugar) and oxygen. The glucose molecules serve as a source of energy for the plant’s growth and development, while the oxygen molecules are released as bubbles.

The evolution of oxygen during photosynthesis is crucial for maintaining a balanced ecosystem. The oxygen released by plants serves as a source of breathable air for humans and other animals. It supports aerobic respiration, a process in which organisms obtain energy from glucose and release carbon dioxide. In addition, photosynthesis plays a crucial role in the global carbon cycle by removing carbon dioxide from the atmosphere and converting it into organic compounds.

When conducting the Hydrilla experiment, it is important to consider possible limitations or sources of error. Factors such as light intensity, water temperature and the health of the hydrilla leaf can influence the rate of photosynthesis and oxygen evolution. To obtain more accurate results, it is important to ensure consistent and controlled conditions throughout the experiment.


The Hydrilla experiment provides students with an engaging and tangible way to understand the process of photosynthesis. By observing the formation of oxygen bubbles on the Hydrilla leaf, students experience first-hand the conversion of light energy into chemical energy and the crucial role of plants in the production of oxygen. This experiment not only deepens their understanding of photosynthesis, but also highlights the importance of plants in maintaining the delicate balance of our ecosystem.

Further Exploration

For those who are curious and want to learn more about photosynthesis, there are several opportunities to experiment and learn further. Students can investigate the effects of different light intensities on the rate of oxygen evolution and compare the results under different light conditions. They can also investigate the effects of temperature or the presence of other aquatic plants on the photosynthetic process.

Also Check – Experimental study on growth of Hydrilla

In addition, students can extend their understanding of photosynthesis by studying other plants and their unique adaptations. They can compare the photosynthetic processes of different aquatic plants, such as Elodea or Vallisneria, to gain a broader perspective on this important biological process.

Remember that photosynthesis is not only crucial for plants, but also for sustaining life on our planet. Studying its mechanisms and effects will deepen our appreciation of the natural world and our role in preserving it.

Also Check – Name the factors affecting Photosynthesis

Also Check – What are the Adaptations of leaf for Photosynthesis

Also Check- 13 Important Differences between Photosynthesis and Respiration

Also Check – Where do Plants get each of the Raw Materials required for Photosynthesis

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