The researchers studied how aging affects the photosynthesis process in cucumber leaves. They found that as the leaves aged, the chlorophyll, protein, and photosystem II activity decreased. Specifically, the photosystem II units and antenna decreased, affecting the plant's ability to absorb light. The binding of a herbicide to the photosystem II protein D1 increased in older leaves, indicating changes in the protein's function. This suggests that as cucumber leaves age, their ability to photosynthesize efficiently decreases.