Stomata in plants control the exchange of water and CO2 with the air. Scientists studied different types of Arabidopsis thaliana plants to see how stomatal density and pattern affect CO2 assimilation. They found that more stomata can increase water loss but not necessarily photosynthesis. Clustering of stomata can reduce their efficiency in transporting CO2. Overall, stomatal density and pattern can impact how plants regulate CO2 and water, but the effect on photosynthesis varies.