Plant cells have a thick waxy cuticle which is transparent to allow sunlight to pass through and it also minimises water loss. There are air spaces in the spongy mesophyll which allows gas exchange to occur (e.g. allows carbon dioxide to enter for photosynthesis to occur). Stomata are located in the lower epidermis which have guard cells which either swell (turgid) to allow gas exchange when the plant has a lot of water or they shrivel (flaccid) when there's not enough water. When the guard cells are flaccid they close the stomata to minimise water loss. There is also a layer of palisade lead cells which have a lot of chloroplast which maximises photosynthesis.