The tissue system of the plant body largely responsible for photosynthesis is the ground tissue system.

Here's why:

* Ground tissue makes up the majority of the plant body. It's found in the roots, stems, and leaves.

* Parenchyma cells, a primary component of ground tissue, are specialized for photosynthesis. They contain chloroplasts, the organelles that house chlorophyll, the pigment that captures light energy.

* Mesophyll, the tissue within leaves where photosynthesis occurs, is primarily composed of parenchyma cells.

While other tissue systems play important roles in plant function, the ground tissue system is the one directly responsible for the primary photosynthetic processes in plants.