The researchers studied how the Japanese knotweed plant's photosynthesis changes throughout the day. They used a portable device to measure different factors like water levels and sunlight. They found that the plant's photosynthesis peaked at 9:00 in the morning. Water levels, stomatal conductance, and transpiration rates were highest at 1:00 in the afternoon. The plant's photosynthesis was mainly limited by factors other than stomatal conductance. Different plant materials showed similar patterns, with tissue-cultured plantlets having the highest photosynthesis. The amount of sunlight was crucial for photosynthesis, affecting it the most. Temperature and other environmental factors mainly influenced photosynthesis through transpiration rates and water levels in the leaves.