Photosynthesis: How The Rate Of O2 Production By Plants Is Affected By Light Exposure Versus No Light Exposure

Photosynthesis is a process that uses sunlight as energy in plants, bacteria, etc. It is a natural process to maintain clean fuels and renewable energy. Photosynthesis is important because most organisms rely on the cells to create molecules. Although the cells are different, they produce carbon dioxide and energy from the sun to make glucose and oxygen molecules. Then, the respiration process uses these cells and molecules to carry new energy cells, known as ATP, and carbon dioxide is coming out as a waste product.

Photosynthesis has two processes called light-independent reaction and light-dependent reactions. In plants, “light” reactions happen when the chloroplast thylakoids while the previous chlorophyll occupy. This happens when a photon of light the reaction center. When light energy enters the molecules, electrons get “excited”. These electrons transport to an electron transport chain in the thylakoid membrane which brings each energy to a low energy state and bring out its energy by producing ATP and NADPH. Each chlorophyll molecule restore its lost electron with an electron from water which splits water molecules to make oxygen.

Since light-dependent reactions produce ATP and NADH, for light-dependent reactions, it is a source of rich energy that drive dark reactions. Light-dependent reactions (Calvin Cycle) have three steps: carbon fixation, reduction, and regeneration which uses water and catalysts. The carbon atoms are built into molecules that form into glucosee. The sugars are used to make glucose or recycled to begin the Calvin Cycle again.

In this investigation, we will use an indicator solution, Bromothymol Blue, to detect the presence or absence of oxygen. Leaf samples will be placed into test tubes containing a solution of carbonated Bromothymol Blue. One test tube will be placed in light for twenty four hours, and the other test tube will be placed in the dark for twenty four hours. At the end of the treatment time, the test tubes will be examined for the presence or absence of oxygen.

Research Question

How is the rate of O2 production by plants affected by exposure to light versus no exposure to light?

II.​ ​Purpose

The purpose of this investigation is to study how the rate of O​2​ production by plants is affected by light exposure versus no light exposure.

III.​ ​Hypothesis

H​o​ (null hypothesis): There will be no difference in outcomes based on different treatments of light vs no light.

H​A​: O​2 ​production will be greater in the light conditions because the reactions that produce O​2 happen only with light exposure.

IV.​ ​Materials

• 2 sprigs of ​Elodea ​(Change to Indian Hawthorn)
• 2 test tubes (Change to 2 Ziploc sandwich bags)
• Distilled water
• Bromothymol Blue (BTB)
• Rubber stoppers
• Environmental light chamber
• Dark cabinet

V. Methods

• Water in the controlled, light, and dark.
• Leaves in the light, controlled, and dark.
• Put it the cabinet or in the light capsule.
• Wait 24 hours.

VI. Results

• Light versus Dark Treatment
• Time (hours) Light Dark Control
• 0 green green green
• 24 blue green green

VII. Discussion and Conclusions

There wasn’t a difference based on the outcomes of the treatments of light vs. no light. Each tube contains the same amount of leaves and water but was hidden in different locations. Based on our experimental results, our Null Hypothesis, H​o​, there will be no similarities in outcomes based on different results of light vs. no light supported. However, our results showed that the alternative hypotheses, H​A​, our production will be more in light conditions because of the reactions that was represented to produce oxygen only happened with light was exposed. When we poured in the water that had carbon dioxide, we sealed it so no air could escape it. Then, we did the same for the rest of the tubes. We selected the same size of leaves in the same three tubes, for better results. We then label the tubes: light, dark, and controlled; to keep track of which is which. Finally, we placed the dark tube in a cabinet for twenty-four hours and the light tube in an environmental light chamber for twenty-four hours.

The scientific concepts that I learned in this investigation is that when we waited for twenty-four hours, the color changed into an emerald green to a faint blue that was hard to notice but against the light you can see the differences. Photosynthesis has taught me that sunlight is necessary for the process to produce oxygen. The oxygen is a waste product for the plants but is essential to us. (​ ​https://www.livescience.com/51720-photosynthesis.html​ ​ ​)

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