Stomata on the surface of a leaf lead to a maze of internal air spaces that expose mesophyll cells to the CO2 they need for photosynthesis (Campbell 2008). The air in these spaces is saturated with water vapor because it is in contact with the humid cell walls (Campbell 2008). Most of the time, the air outside the leaf is drier; that is, it has a lower water potential than the air inside the leaf (Campbell 2008). Therefore, water vapor present in the air spaces of a leaf diffuses along its water potential gradient and exits the leaf through the stomata (Campbell 2008). This loss of water vapor from the leaf and evaporation is called transpiration (Kimball 1994). Transpiration is a process by which water from plants is lost to the atmosphere (Cooke 2012). This is extremely costly to the plant, especially when water supplies are limited (McElrone 2013). Water loss through transpiration may be facilitated by the opening and closing of stomata depending on environmental conditions (Kimball 1994). Stomata are pores located on the epidermis below the leaf surface that regulate gas exchange between the interior of the leaf and the atmosphere (McElrone 2013). They are located on the lower surface to help the plant reduce the amount of water loss due to the absence of direct solar radiation (Cooke 2012). Stomata are known as pumps that extract nutrients and water from the roots down to the leaves; this process is known as transpirational attraction (Cooke 2012). Transpirational attraction drives water flow in the plant due to the phenomenon of water potential (Campbell 2008). The negative pressure potential causes water to move through the xylem to the surface of the leaf's mesophyll cell walls (Campbell 20...... middle of paper ...... o have different Mass measurements over time. Humidity in the plant's surrounding atmosphere will cause the plant to sweat the least because its constant exposure to water will allow the plant to stay hydrated and release a small percentage of water (Wallace). 1962), knowing that light has a major effect on the rate of photosynthesis, if the plant has been placed under high power light, it will then have a higher rate of transpiration because the stomata will remain open due to gas exchange. resulting from photosynthesis (Klekowski 1997 to decrease and result in a high transpiration rate due to being in a drier environment (McElrone 2013). The pH level variable will vary depending on their result as the plant. will react differently when exposed to very acidic or basic soil (McElrone 2013). 2013).