The researchers studied how Angelica sinensis plants photosynthesize during the day and how environmental factors like sunlight, temperature, and humidity affect this process. They found that the plants have two peaks of photosynthesis at 10:00 and 16:00, with a dip around noon. Stomatal conductance plays a big role in this midday dip. The amount of sunlight and leaf temperature have the biggest impact on photosynthesis, while other factors like CO2 levels and humidity indirectly affect it through temperature.