How does global warming effect photosynthesis?

Even though global warming is largely brought about by increased CO2 and increased CO2 can actually increase the rate of photosynthesis, researchers have shown that overall photosynthesis diminishes with rises in air temperature. During the process of transpiration, plants lose water through tiny holes in their leaves called stomata. Because the water evaporates from the surface of the leaf, transpiration helps plants stay cool, in the same way perspiration keeps humans and animals cool. So the process of plants losing water through their stomata prevents overheating of the plant. When less water from the soil is available, the plant closes the stomata on its leaves so water doesn't escape from the plant. Unfortunately, closed stomata don't let in necessary CO2 for photosynthesis and plant growth becomes stunted -- the plant must now choose between keeping its own water (stomata closed) and gaining food (stomata open). At the point when the plant cannot survive any more without food, it will be forced to open its stomata, letting its own water escape. The plant, which is fighting to survive, becomes wilted or withered. Many plants, especially grain crops that feed the people of our world are susceptible to warmer temperatures and dryer conditions/drought brought on by climate change. Our hope is that science, research and technology will bring about feast and not famine as we pore over these issues and figure out new and innovative solutions to the challenges set before us.