# I'm having wayyy tooo much trouble with this simple assignment.

Is there a lab that proves that the light reactions must occur prior to the dark reactions in photosynthesis?

So far, I thought of the experiment in which one plant is placed in direct sunlight and the other is placed inside a box. The two conditions constant (i.e. same type of plant, same amounts of water) apart from the lack of sunlight received by the second plant in the box. But would this experiment really prove that the light reactions occur first?? And if so, would weighing the mass of the plants indicate the information necessary to show that light reactions must occur first?

## To determine whether the light reactions must occur prior to the dark reactions in photosynthesis, you can conduct an experiment similar to the one you described. However, measuring the mass of the plants alone may not provide conclusive evidence.

Here's an experiment that can help you demonstrate the order of reactions:

1. Select two identical plants of the same species.
2. Place one plant in direct sunlight and the other in a box without any light source. Ensure that the other conditions (such as water, temperature, and nutrients) are the same for both plants.
3. Leave the plants undisturbed for a designated period, such as 24 hours.
4. After the designated period, harvest both plants and separate the leaves.
5. Carry out a starch test on the leaves. This test will detect the presence of starch, which indicates that photosynthesis has occurred.
6. Perform the starch test on the leaves of both plants using iodine solution.
a. Dip the leaves in boiling water to soften them.
b. Place the leaves in a dish and cover them with iodine solution.
c. Observe the color change in the leaves: blue-black color indicates the presence of starch, while a brownish color indicates the absence of starch.
d. Compare the results between the two plants.

If the plant exposed to direct sunlight shows a blue-black color change, indicating the presence of starch, and the plant in the box shows a brownish color change, indicating the absence of starch, it suggests that the light reactions must occur before the dark reactions. The sunlight-exposed plant was able to carry out photosynthesis, while the plant in the box, deprived of light, was not.

Measuring the mass of the plants can provide additional data, such as changes in growth rates or biomass production. However, it alone doesn't confirm the order of reactions. The starch test is a more direct method for showing the occurrence of photosynthesis.

Remember, scientific experiments are subject to variables and limitations. Designing multiple, well-controlled experiments and repeating them can help strengthen your results and conclusions.