Murfreesboro is a city in Pike County, Arkansas, United States. The population was 1,764 at the 2000 census. The city is the county seat of Pike County. Crater of Diamonds State Park is located just to the south. The crater is an eroded lamproite pipe where diamonds were discovered in 1906. 100,000 were found by 1933, and visitors to the park may still take away whatever they can find.
The guard cells surround each stoma in a plant cell. They regulate  the opening and closing of stomata to facilitate gas exchange and  control transpiration in plants.
Guard cells have a special structure that helps them to open and close. The aim of the process is to control the amount of water getting outside the plant in case of water stress. When guard cells open CO2 gets in for the process of photosynthesis to take place..Water gets out the leaf from the stomata through transpiration. So, for CO2 to get in for the plant to photosynthesize food, water gets out. As if the plant is paying water as a currency for taking in CO2.