The amount of water that plants give up depends on how much carbon dioxide is present in the atmosphere. This makes them have a significant role in our Earth's water cycle. All plants draw in water out of the atmosphere and soil, and they discharge water vapor and oxygen into the air through transpiration. Studies have shown that the plants pores, or stomata, are changing with rising co2 levels. The leaf pores contract and sometimes close to conserve the water. This is increasing water efficiency and reducing the rate of transpiration. When these plant release less water they are also taking less out of the environment. Since less water is being absorbed more water is going to groundwater or is running into bodies of water. When this water is making its way to the bodies of water it is collecting excess nutrients and pollutants. Then this enters the lakes, rivers, and streams and affecting the health of fish, algae, and shellfish. It is also contaminating our drinking water and beaches. The excess runoff also contributes to some flooding. It is found that for every molecule of CO2 the plants take in, they lose 44 percent less water.
http://www.sciencedaily.com/releases/2009/07/090709120657.htm
1. Plants breathe in CO2 through microscopic pores on their leaves.
2. 1 molecule of CO2 inhaled = 100’s of molecules of H20 lost.
3. (Optional) Plants can tighten those pores to save water.