Does Photosynthesis happen mainly in the palisade cells in the roots?

No, photosynthesis does not mainly occur in the palisade cells in the roots. Photosynthesis primarily takes place in the leaves of plants, particularly in the palisade mesophyll cells, which are rich in chloroplasts. Roots typically absorb water and nutrients from the soil, and they do not contain chlorophyll, so they do not carry out photosynthesis.