The researchers studied the different types of chlorophyll in tobacco plants to understand how they help with photosynthesis. They looked at the chloroplasts of normal plants and mutants with higher levels of certain chlorophylls. They found that Photosystem I absorbs light at 678 nm, while Photosystem IIα uses chlorophyll a and b to absorb light at 650 and 672 nm. The mutants had more chlorophyll a than b in their light-harvesting complex. Overall, they discovered the specific chlorophyll forms present in each photosystem and how they contribute to plant energy production.