The researchers studied how the photosynthesis of Pinus strobus leaves changes throughout the day. They used a portable photosynthetic system to measure the net photosynthetic rate, transpiration rate, and stomata conductance. The results showed that the photosynthesis rate of the leaves had two peaks during the day, with a decrease in efficiency at midday. The transpiration rate followed a similar pattern to photosynthesis, but peaked at a different time. Stomata conductance also showed a similar trend to photosynthesis, but reached its maximum two hours earlier.