CIMAHI, WEST JAVA – Students of Grade IX at SMPN 3 Cimahi, West Java, were asked to conduct an experiment on photosynthesis with the plant Hydrilla verticillata (10/10). This lesson aimed to teach students to observe the phenomenon of photosynthesis and present their observations. They were guided by their teacher, Lien S. The lesson started with the teacher explaining to the students about a 40-year-old Tradescantia plant growing in a bottle. Despite only getting water once, the plant can still grow thanks to sunlight. The process of photosynthesis produces the energy the plant needs to grow.
The phenomenon of photosynthesis produces oxygen and water droplets which then serve as the "rain" in the bottle. How does light influence the speed of photosynthesis in the Hydrilla verticillata plant? The students were encouraged to express their opinions and prove this hypothesis by conducting an experiment.
Working enthusiastically in their groups, the students performed the Jan Ingenhousz experiment to prove that photosynthesis produces oxygen. One piece of apparatus is placed under direct sunlight and another in a room where it is not exposed to light. If the school doesn't have the apparatus, simple apparatus made from waste materials can be used, such as mineral water bottles; test tubes for holding the oxygen can be replaced with small pieces of plastic hose.
The children were excited and even applauded when they saw the air bubbles appear in the test tube. They were excited when they recorded the number of air bubbles. With the appearance of these bubbles the children's experiment was successful. The bubbles accumulate at the bottom of the test tube and formed air cavities.
The gas in the bubbles was tested by using the embers of burnt palm leaf ribs. A flame will light if there is oxygen present. To prove that the collected air bubbles contained oxygen, the students put the embers near the mouth of the test tube.
The embers of the palm leaf ribs produced flames. This proves that the gas produced by the process of photosynthesis was oxygen. The embers caught fire when placed near the mouth of the test tube containing the gas from photosynthesis. (Ds)