The experiment is used to demonstrate that

The experiment is used to demonstrate that transpiration occurs through the leaves. Transpiration is the process by which plants lose water vapor through tiny pores called stomata, which are primarily located on the leaves. In this experiment, water is added to the plant's soil or roots, and then the plant is covered with a plastic bag, which causes the humidity inside the bag to increase. As a result, the water vapor released by transpiration will accumulate inside the bag, forming droplets. This shows that transpiration is occurring through the leaves, as the bag prevents water loss from other parts of the plant. This experiment does not directly demonstrate that water is necessary for photosynthesis or that leaves are important to photosynthesis, although these are both true statements. It also does not demonstrate guttation, which is a different process by which water is exuded from the tips of leaves.