BACKGROUND: Photosynthesis takes place in green plants in specialized structures called chloroplasts. For photosynthesis to occur, the chloroplasts must be exposed to sufficient light. Today's sample work will examine whether the amount of light can have an impact on how quickly photosynthesis takes place.
The green plant used in the videos is called elodea. It is important to note that some types of elodea are invasive, so stores in South Carolina are legally limited regarding the sale of elodea. Most stores in our state will not sell any type of elodea because it is very easy to mix up the invasive type with the noninvasive type. If you ever encounter elodea from a pet store, it is very important that you dispose of it properly. Elodea should be sealed in a plastic bag and frozen for at least 72 hours before discarding in a proper trash receptacle, still sealed in the plastic bag.
Refresh your memory regarding the chemical equation that summarizes the process of photosynthesis. As a reminder, reactants are on the left side of the equation, and products are on the right side of the equation.
For this experiment, pieces of elodea have been placed in water that was aged (allowed to sit for a few days so the chlorine in it will evaporate away) and treated with baking soda (so it will have plenty of carbon dioxide). For the first part of the experiment, the elodea will be in a low light condition. For the second part of the experiment, the elodea will be in a high light condition. In both cases, as the plant absorbs sunlight, it will perform photosynthesis. Oxygen gas bubbles will be released, especially from the stem (due to the plant's orientation in the water). The rate at which oxygen gas bubbles are produced is an indicator of how quickly photosynthesis is taking place.
EXPERIMENTAL QUESTION: How will changing the amount of light affect the rate of photosynthesis?
HYPOTHESIS: Increasing the amount of light will increase the rate of photosynthesis.
MATERIALS: beaker, lamp, elodea plant, aged tap water with baking soda added, timer
Question
1. Which prediction for the number of bubbles produced best matches the stated hypothesis?(1 point)
Responses
The low light condition is predicted to result in more bubbles than the high light condition.
The low light condition is predicted to result in more bubbles than the high light condition.
The high light condition is predicted to result in more bubbles than the low light condition.
The high light condition is predicted to result in more bubbles than the low light condition.
The low light and high light conditions are predicted to produce the same amount of bubbles.
1 answer
The prediction that best matches the stated hypothesis ("Increasing the amount of light will increase the rate of photosynthesis") is:
The high light condition is predicted to result in more bubbles than the low light condition.
This aligns with the hypothesis because if more light is available, the rate of photosynthesis, indicated by the production of oxygen bubbles, is expected to increase.
