These epidermis cells don't contain chloroplasts.
Their function function is to protect the inner layers of cells in the leaf.
They do not have chloroplasts, so light passes easily through them.
The cells of the upper epidermis is often secrete a waxy substance, that lies on top of them.
It is called cuticle and it helps to stop water evaporating fro the leaf.
Palisade cells are packed together and filled with chloroplasts.
Best site for photosynthesis since light penetrates, carbon dioxide and water are delivered and chlorophyll is present.
Gas exchange happens in the spongy mesophyll tissue of the leaf.
Spongy mesophyll cells are covered by a thin layer of water and loosely packed.
When the plant is photosynthesising during the day, these features allow carbon dioxide to diffuse into the spongy mesophyll cells, and oxygen to diffuse out of it.
To get to the spongy mesophyll cells inside the leaf, gases diffuse through small pores called stomata.
They also open or close to control the loss of water from leaf by the process of transpiration.