Our biology laboratory transformed into an underwater observation deck this week as students dove into the mechanics of photosynthesis using Ceratophyllum demersum, commonly known as hornwort.
This experiment offered a rare, real-time look at how aquatic plants process energy. By placing these submerged plants under bright light sources, students were able to witness the chemical process of photosynthesis in action—quite literally, by watching the plant "breathe."
The Experiment: Inputs and Outputs
To understand how plants transform environmental resources into life-sustaining energy, students tracked the journey of specific inputs and outputs.
Diagram showing process of photosynthesis with plant and cells
In the lab, the hornwort served as a model organism. The process is defined by the transformation of light energy and inorganic matter into chemical energy:
The Inputs: The students identified three critical components required for the reaction:
Light Energy: Captured by the plant's chloroplasts.
Water : Absorbed directly from the surrounding aquatic environment.
Carbon Dioxide: Dissolved in the water, which the plant utilizes for carbon fixation.
The Outputs: As the light hit the hornwort, students observed the visible proof of the reaction:
Oxygen: This was the highlight of the lab. Students watched as tiny oxygen bubbles formed on the leaves and stems of the hornwort, escaping into the water.
Glucose: While invisible to the naked eye, the production of these sugars serves as the primary chemical energy source for the plant's growth.
By observing the bubbles of oxygen—a byproduct of the splitting of water molecules—students gained a deeper appreciation for the complex interplay between light, water, and gas exchange.