20 ! answer ! a plant releases water through the stomata in its leaves. as water evaporates from the leaves, more water is pulled up from roots through the stem and into the leaves. this process is called transpiration and allows the plant to pull needed water and nutrients from the soil. you decide to do an experiment to determine how much water a plant can take up in a certain amount of time. what is your tested or measured variable? what are your controlled variables or what factors do you need to hold constant?