A C4 plant is any plant that produces oxaolacetic acid on the first step of photosynthesis. This acid contains four carbon atoms. C4 plants need 30 molecules of ATP and 24 molecules of water to produce a single molecule of glucose. Being a C4 plant gives it the ability to continue to photosynthesize in low carbon dioxide concentrations and at high light intensities. Also, C4 plants prevent photorespiration. Corn plants are an example of C4 plants that is why corn is pictured.