Final answer:
Photosynthesis takes place primarily in the mesophyll, specifically in the palisade parenchyma where chloroplasts are abundant.
Step-by-step explanation:
In plants, photosynthesis takes place primarily in the mesophyll, a middle layer of the leaf.
The mesophyll consists of two arrangements of parenchyma cells: the upper palisade parenchyma and the lower spongy parenchyma.
The majority of photosynthesis occurs in the palisade parenchyma, where tightly packed, column-shaped cells contain numerous chloroplasts.