Leaf color affects how well poplar trees can photosynthesize. A study compared red and green leaf poplars and found that the red leaf poplar absorbed light and CO2 well, especially in low light. However, as light and CO2 levels increased, both types of poplars had limited photosynthetic capacity. The red leaf poplar had lower photosynthetic rates under high light or CO2 conditions due to differences in stomatal regulation and photosynthetic efficiency. The red leaf poplar had higher anthocyanin levels, which decreased its photosynthetic efficiency. The green leaf poplar had better capture efficiency of light energy and higher levels of QA-, which affected its photosystem II performance. Differences in gene expression also played a role in these photosynthetic processes.