Researchers studied how different layers of alfalfa leaves in the Loess Plateau absorb sunlight and produce energy through photosynthesis. They found that upper leaves have the highest photosynthetic capacity, while lower leaves are limited in their ability to capture light energy. The middle layer of leaves falls between the upper and lower layers in terms of photosynthetic activity. The study suggests that factors controlling photosynthesis change throughout the day, with stomatal factors playing a role before peak sunlight and non-stomatal factors becoming more important later on.