Adding food dye to potted or cut plants is a simple biology experiment that shows the effects of transpiration in plants. Transpiration is a process in which plants absorb water, from either a vase or soil, and evaporate it through its stomata, located in the leaf and stem. Adding food dye or food coloring to plants provides no negative or positive contributions to plant growth. However, it does demonstrate the plants ability to soak up nutrients and water.
A popular experiment to determine the effects of food dye on plants is with white daisies. According to the North Carolina State University, white daisies placed in a water-filled vase with plenty of food dye will soak up the water and dye, thus turning the white flowers, stems and leaves the same color as the dye. The same experiment works on potted plants by adding a substantial amount of food dye to water before adding the water to soil. However, much more food dye is necessary for a substantial change in flower color for potted plants. Using food coloring to change the color of a plant is also popular among florists and home growers to change the color of a plant. However, the United States Department of Energy NEWTON states that some plants, even ones with white flowers, are not susceptible to dyeing.
According to the North Carolina State University, dyeing plants with food coloring shows the effects of pollution on plants. Food dye is an outside source or contaminant to the water with no nutritional value; however, it is still absorbed throughout the stem, leaves and flower of the plant. Like the food dye, pollutants in the water and soil are absorbed through the plant during the process of transpiration.
Transpiration is the way in which a plant absorbs water from its root system to the stem and leaves, where it then changes to a vapor through evaporation. Although an invisible process, leaves can transpire many times over their own weight in water each year. For example, according to the United States Geological Survey , an oak tree can transpire over 40,000 gallons of water per year. The food dye experiment can take several days for results; however, the change in plant color shows the effects of the plant absorbing significant portions of water through the process of transpiration. The Cornell University recommends observing the change in color in the stem, as that is the area that brings water from the soil or vase to the rest of the plant.